Communication apparatus and communication method

ABSTRACT

Modulated signal A is transmitted from a first antenna, and modulated signal B is transmitted from a second antenna. As modulated signal B, modulated symbols S 2 ( i ) and S 2 ( i +1) obtained from different data are transmitted at time i and time i+1 respectively. In contrast, as modulated signal A, modulated symbols S 1 ( i ) and S 1 ( i )′ obtained by changing the signal point arrangement of the same data are transmitted at time i and time i+1 respectively. As a result the reception quality can be changed intentionally at time i and time i+1, and therefore using the demodulation result of modulated signal A of a time when the reception quality is good enables both modulated signals A and B to be demodulated with good error rate performances.

This is a continuation application of application Ser. No. 12/697,878filed Feb. 1, 2010, which is a continuation of Ser. No. 10/562,932 filedDec. 30, 2005, which is a national stage of PCT/JP2004/009774 filed Jul.2, 2004, which is based on Japanese Application No. 2003-190683 filedJul. 2, 2003 and Japanese Application No. 2004-173224 filed May 14,2004, the entire contents of each which are incorporated by referenceherein. The following is a co-pending related continuation application:application Ser. No. 12/824,047 filed Jun. 25, 2010.

TECHNICAL FIELD

The present invention relates in particular to a communication apparatusand communication method that use multiple antennas.

BACKGROUND ART

An example of a conventional communication method that uses multipleantennas is the communication method known as MIMO (Multiple-InputMultiple-Output). In multi-antenna communication represented by MIMO aplurality of streams of transmit data are individually modulated, andeach modulated signal is transmitted simultaneously from a differentantenna, thereby increasing the data communication speed.

In this kind of communication method, the receiving side must separateand demodulate a plurality of modulated signals multiplexed together onthe transmission path. Therefore, in communication using multipleantennas, demodulation precision has a major influence on the effectivedata transmission speed.

An example of a heretofore known technology that improves modulatedsignal reception quality on the receiving side and improves theeffective data transmission speed when performing multi-antennacommunication is a technique whereby space-time block codes aretransmitted as described in “Space-Time Block Codes from OrthogonalDesign” IEEE Transactions on Information Theory, pp. 1456-1467, vol. 45,no. 5, July 1999.

These space-time block codes will be explained briefly using FIG. 1. Asshown in FIG. 1B, a transmitting apparatus has antennas 5 and 6, andtransmits a signal simultaneously from each of antennas 5 and 6. Areceiving apparatus receives the simultaneously transmitted plurality ofsignals with an antenna 7.

FIG. 1A shows the frame configuration of signals transmitted fromantennas 5 and 6. A transmit signal A is transmitted from antenna 5, andat the same time, a transmit signal B is transmitted from antenna 6.Transmit signal A and transmit signal B are composed of symbol blocks inwhich the same symbols are placed a plurality of times so that codinggain and diversity gain are obtained.

This will now be explained in more detail, In FIG. 1A, S1 and S2indicate different symbols, and complex conjugates are indicated by “*”.In space-time block coding, at time i, symbol S1 is transmitted fromfirst antenna 5 and symbol −S2* is simultaneously transmitted fromsecond antenna 6, and then at time i+1, symbol S2 is transmitted fromfirst antenna 5 and symbol S1* is simultaneously transmitted from secondantenna 6.

At antenna 7 of the receiving apparatus, a signal is received in whichtransmit signal A subjected to channel fluctuation h1(t) between antenna5 and antenna 7, and transmit signal B subjected to channel fluctuationh2(t) between antenna 6 and antenna 7, are combined.

The receiving apparatus estimates channel fluctuations h1(t) and h2(t),separates the original transmit signal A and transmit signal B from thecomposite received signal by using those estimates, and then demodulatesthe symbols.

If space-time block coded signals are used at this time, when signalseparation is carried out maximal-ratio combining of symbols S1 and S2can be performed regardless of channel fluctuations h1(t) and h2(t),enabling large coding gain and diversity gain to be obtained. As aresult, reception quality—that is, error rate performances can beimproved.

As a different modulated signal is transmitted from each transmittingantenna in multi-antenna communication as described above, it is ideallypossible for the data transmission speed to be increased by a factorequal to the number of antennas compared with a case where a modulatedsignal is transmitted from a single antenna. However, if the precisionof separation and demodulation of the modulated signals is poor, theeffective data transmission speed will decrease.

In contrast, when space-time block coding technology is used, thereception quality (error rate performances) of the modulated signaltransmitted from each antenna can be improved, enabling a decrease indata transmission speed due to degradation of separation anddemodulation precision to be suppressed.

However, a drawback with the use of space-time block coding technologyis that, while reception quality (error rate performances) certainlyimproves, transmission efficiency decreases. That is to say, since S1*and −2* transmitted using space-time block coding are demodulated as S1and S2 by the receiving apparatus, the same information is transmittedtwice at time i and time i+1, and transmission efficiency decreasesproportionally.

For example, in a general multi-antenna communication system, symbols S3and S4 differing from symbols S1 and S2 are transmitted at time i+1, andtherefore four symbols S1 through S4 can be transmitted in the periodfrom time i to time i+1. That is to say, considered in simple terms,data transmission efficiency when using space-time block codingtechnology decreases to half that of general multi-antennacommunication.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a communicationapparatus and communication method that enable excellent receptionquality to be obtained while suppressing a decrease in data transmissionefficiency.

In order to achieve this object, when a first modulated signal istransmitted from a first antenna and a second modulated signal istransmitted from a first antenna, the signal point arrangement mode ofat least one modulated signal of the first modulated signal and secondmodulated signal is changed in the time direction or the frequencydirection.

By this means, the modulated-signal signal point arrangement changes foreach time or each subcarrier, and therefore, on the receiving side, theEuclidian distance between a candidate signal point and reception pointis large at a particular time or in a particular subcarrier, and theEuclidian distance between a candidate signal point and reception pointis small at a particular time or in a particular subcarrier. As aresult, a diversity effect can be obtained, and reception quality can beimproved.

Also, in the present invention, the first modulated signal is formed bymodulating the same data of first transmit data a plurality of timeswhile changing the signal point arrangement mode, and the secondmodulated signal is formed by modulating second transmit data withoutchanging the signal point arrangement mode.

By this means, the demodulation result of a first modulated signalobtained based on a received signal of a time or subcarrier of goodreception quality can be made a first modulated signal received digitalsignal, a received digital signal of a second modulated signal receivedat a time or in a subcarrier of poor reception quality can be obtainedfrom a received signal of that time or subcarrier of poor receptionquality using a received digital signal of the first modulated signal ofa time or subcarrier of good reception quality already determined, andthe error rate performances of the second modulated signal received at atime or in a subcarrier of poor reception quality can also be improved.As a result, a received digital signal with good error rate performancescan be obtained for both the first modulated signal and the secondmodulated signal.

Moreover, in the present invention, a modulated signal formed fromdifferent transmit data is basically transmitted from each antenna,enabling a decrease in data transmission efficiency to be suppressed toa greater extent than when space-time block coding is used.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a drawing showing an example of the frame configurations ofconventional transmit signals;

FIG. 1B is a drawing showing the relationship between transmittingantennas and a receiving antenna;

FIG. 2A is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 1;

FIG. 2B is a drawing showing the relationship between transmittingantennas and receiving antennas;

FIG. 3A through FIG. 3C are drawings showing sample signal pointarrangements according to Embodiment 1;

FIG. 4 is a block diagram showing a sample configuration of atransmitting apparatus according to Embodiment 1;

FIG. 5 is a block diagram showing a sample configuration of a modulationsection according to Embodiment 1;

FIG. 6 is a block diagram showing a sample configuration of a receivingapparatus according to Embodiment 1;

FIG. 7 is a block diagram showing a sample configuration of ademodulation section according to Embodiment 1;

FIG. 8 is a block diagram showing another sample configuration of ademodulation section;

FIG. 9 is a drawing showing sample frame configurations according toEmbodiment 1;

FIG. 10A and FIG. 10B are drawings showing sample frame configurationsaccording to Embodiment 1;

FIG. 11A through FIG. 11C are drawings showing sample signal pointarrangements according to Embodiment 1;

FIG. 12 is a drawing showing a sample configuration of a demodulationsection according to Embodiment 1;

FIG. 13 is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 1;

FIG. 14 is a drawing showing a reception state according to Embodiment1;

FIG. 15 is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 2;

FIG. 16 is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 2;

FIG. 17 is a drawing showing the relationship between transmitting andreceiving antennas according to Embodiment 2;

FIG. 18 is a block diagram showing a sample configuration of atransmitting apparatus according to Embodiment 2;

FIG. 19 is a block diagram showing a sample configuration of a receivingapparatus according to Embodiment 2;

FIG. 20 is a block diagram showing a sample configuration of ademodulation section according to Embodiment 2;

FIG. 21 is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 2;

FIG. 22 is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 2;

FIG. 23 is a block diagram showing a sample configuration of atransmitting apparatus according to Embodiment 2;

FIG. 24 is a block diagram showing a sample configuration of ademodulation section according to Embodiment 2;

FIG. 25 is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 2;

FIG. 26 is a drawing showing sample frame configurations of modulatedsignals according to Embodiment 2;

FIG. 27 is a block diagram showing a sample configuration of atransmitting apparatus according to Embodiment 3;

FIG. 28 is a block diagram showing a sample configuration of a receivingapparatus according to Embodiment 3;

FIG. 29A and FIG. 29B are drawings showing sample frame configurationsof modulated signals according to Embodiment 1;

FIG. 30A and FIG. 30B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 31A and FIG. 31B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 32A and FIG. 32B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 33A and FIG. 33B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 34A and FIG. 34B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 35A and FIG. 35B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 36A and FIG. 36B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 37A and FIG. 37B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 38A and FIG. 38B are drawings showing sample frame configurationsof modulated signals according to Embodiment 3;

FIG. 39A through FIG. 39C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 40A through FIG. 40C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 41A through FIG. 41C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 42A through FIG. 42C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 43A through FIG. 43C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 44A through FIG. 44C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 45A through FIG. 45C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 46A through FIG. 46C are drawings showing sample frameconfigurations of modulated signals according to Embodiment 3;

FIG. 47A and FIG. 47B are drawings provided to explain interleavingaccording to Embodiment 4;

FIG. 48A through FIG. 48C are drawings showing sample signal pointarrangements according to Embodiment 4;

FIG. 49 is a block diagram showing a sample configuration of atransmitting apparatus according to Embodiment 4;

FIG. 50 is a block diagram showing a sample configuration of amodulation section according to Embodiment 4;

FIG. 51 is a block diagram showing a sample configuration of a receivingapparatus according to Embodiment 4;

FIG. 52A is a drawing showing a reception signal point state in whichthe minimum Euclidian distance is small and reception quality is poor;

FIG. 52B is a drawing showing a reception signal point state in whichthe minimum Euclidian distance is large and reception quality is good;

FIG. 53A and FIG. 53B are drawings showing sample signal pointarrangements according to Embodiment 4;

FIG. 54A is a drawing showing a reception signal point state in whichthe minimum Euclidian distance is small and reception quality is poor;

FIG. 54B is a drawing showing a reception signal point state in whichthe minimum Euclidian distance is large and reception quality is good;

FIG. 55 is a block diagram showing a sample configuration of a basestation according to Embodiment 5;

FIG. 56 is a block diagram showing a sample configuration of acommunication terminal according to Embodiment 5; and

FIG. 57 is a block diagram showing a multi-beam MIMO system as a sampleapplication of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the accompanying drawings, embodiments of thepresent invention will be explained in detail below.

(1) Embodiment 1

In this embodiment it is proposed that, when a first and second antennaare used and a different modulated signal is transmitted from eachantenna, the same data be transmitted a plurality of times for only onemodulated signal. In this embodiment, two modulated signals are formedby modulating two different streams of data, and these two modulatedsignals are transmitted from different antennas. At this time, in amodulated signal transmitted from one of the antennas, the same data istransmitted a plurality of times, changing the signal point arrangementmode. By this means, since different modulated signals are basicallytransmitted from each antenna, the error rate performances of datatransmitted a plurality of times can be improved, and as a result, theerror rate performances of both streams (the two streams) can beimproved, while maintaining a higher data transmission speed than whenspace-time block coding is used.

FIG. 2A shows frame configurations of modulated signals transmitted froma communication apparatus according to Embodiment 1 of the presentinvention. Modulated signal A and modulated signal B are transmittedfrom different antennas. Modulated signals A and B contain radio wavepropagation environment estimation symbols 101 and 104 respectively.Radio wave propagation environment estimation symbols 101 and 104 arepredetermined symbols for estimating the radio wave propagationenvironment in a receiving apparatus.

Reference codes 102, 103, 105, and 106 denote data symbols. Modulatedsignal A point i data symbol 102 (S1(i)) and modulated signal A pointi+1 data symbol 103 (S1(i)′) form the same data as signal pointarrangements with the mapping rule changed. On the other hand, modulatedsignal B point i data symbol 105 (S2(i)) and modulated signal B pointi+1 data symbol 106 (S2(i+1)) have mutually different data that hasundergone signal point arrangement in accordance with the same mappingrule. That is to say, while modulated signal B is a typical modulatedsignal, modulated signal A transmits the same data a plurality of times,changing the mapping pattern.

In FIG. 2B, modulated signal A is transmitted from transmitting antenna107 and modulated signal B is transmitted from transmitting antenna 108.Then a signal combining modulated signal A and modulated signal Bmultiplexed together on the propagation path is received at each ofreceiving antennas 109 and 110.

FIG. 3A through FIG. 3C show sample signal point arrangements formodulated signal. A. FIG. 3A shows the signal point arrangement ofsymbol 102 in FIG. 2, FIG. 3B and FIG. 3C show signal point arrangementsof symbol 103 in FIG. 2. FIG. 3B is an example in which the same data isarranged with the phase rotated through 90° with respect to the signalpoint arrangement in FIG. 3A. FIG. 3C is an example in which the samedata is arranged with the phase rotated through 45° with respect to thesignal point arrangement in FIG. 3A.

FIG. 4 shows a sample configuration of a transmitting apparatusaccording to this embodiment. The transmitting apparatus in FIG. 4mainly comprises a coding section 302, a modulation section 304, aspreading section 306, a radio section 308, a power amplifier 310, amodulation section 314, a spreading section 316, a radio section 318, apower amplifier 320, and a frame configuration signal generation section323.

In FIG. 4, frame configuration signal generation section 323 outputs asignal frame configuration signal 324 indicating a frameconfiguration—for example, information indicating which symbol in aframe is to be transmitted. Based on signal frame configuration signal324, coding section 302 outputs a transmit digital signal 301 aplurality of times (in this embodiment, twice) in symbol units as apost-coding digital signal 303.

Modulation section 304 has post-coding digital signal 303 and frameconfiguration signal 324 as input, and outputs a transmit quadraturebaseband signal 305 to spreading section 306. At this time, modulationsection 304 performs modulation by mapping information in apredetermined signal point arrangement as shown in FIG. 3A, and thenperforms modulation by mapping the same information in a differentsignal point arrangement from the previous time as shown in FIG. 3B andFIG. 3C.

Spreading section 306 spreads transmit quadrature baseband signal 305and outputs a post-spreading transmit quadrature baseband signal 307 toradio section 308. Radio section 308 converts post-spreading transmitquadrature baseband signal 307 from baseband frequency to radiofrequency, and outputs a post-conversion modulated signal 309 to poweramplifier 310. Power amplifier 310 amplifies the power of modulatedsignal 309, and outputs a post-amplification modulated signal 311.Modulated signal 311 is output from antenna 107 as a radio wave.

Modulation section 314 has transmit digital signal 313 and frameconfiguration signal 324 as input, and outputs transmit quadraturebaseband signal 315. Spreading section 316 spreads transmit quadraturebaseband signal 315, and outputs post-spreading transmit quadraturebaseband signal 317.

Radio section 318 converts post-spreading transmit quadrature basebandsignal 317 from baseband frequency to radio frequency, and outputs apost-conversion modulated signal 319. Power amplifier 320 amplifies thepower of modulated signal 319, and outputs a post-amplificationmodulated signal 321. Modulated signal 321 is output from antenna 108 asa radio wave.

FIG. 5 shows a sample configuration of modulation section 304 in FIG. 4according to this embodiment. In FIG. 5, a mapping section X 402 has apost-coding digital signal 303 and frame configuration signal 324 asinput, and by mapping digital signal 303 as shown in FIG. 3A, outputs afirst mapped transmit quadrature baseband signal 403.

A mapping section Y 404 has post-coding digital signal 303 and frameconfiguration signal 324 as input, and by mapping digital signal 303using a different mapping pattern from that of mapping section X 402 asshown in FIG. 3B or FIG. 3C, outputs a second mapped transmit quadraturebaseband signal 405.

A signal selection section 407 has first mapped transmit quadraturebaseband signal 403, second mapped transmit quadrature baseband signal405, and frame configuration signal 324 as input, selects eithertransmit quadrature baseband signal 403 or transmit quadrature basebandsignal 405 based on the frame configuration signal, and outputs selectedtransmit quadrature baseband signal 305.

FIG. 6 shows a sample configuration of a receiving apparatus accordingto this embodiment. A radio section 503 has a received signal 502received by an antenna 109 as input, and outputs a received quadraturebaseband signal 504. A despreading section 505 has received quadraturebaseband signal 504 as input, and outputs a post-despreading receivedquadrature baseband signal 506.

A modulated signal A transmission path estimation section 507 haspost-despreading received quadrature baseband signal 506 as input,estimates modulated signal channel fluctuation (h11(t) in FIG. 2B) basedon radio wave propagation environment estimation symbol 101 contained inmodulated signal A (FIG. 2A), and outputs the estimation result as amodulated signal A transmission path estimation signal 508. Similarly, amodulated signal B transmission path estimation section 509 haspost-despreading received quadrature baseband signal 506 as input,estimates modulated signal B channel fluctuation (h21(t) in FIG. 2B)based on radio wave propagation environment estimation symbol 104contained in modulated signal B (FIG. 2A), and outputs the estimationresult as a modulated signal B transmission path estimation signal 510.

A radio section 513 has a received signal 512 received by an antenna 110as input, and outputs a received quadrature baseband signal 514. Adespreading section 515 has received quadrature baseband signal 514 asinput, and outputs a post-despreading received quadrature basebandsignal 516.

A modulated signal A transmission path estimation section 517 haspost-despreading received quadrature baseband signal 516 as input,estimates modulated signal channel fluctuation (h12(t) in FIG. 2B) basedon radio wave propagation environment estimation symbol 101 contained inmodulated signal A (FIG. 2A), and outputs the estimation result as amodulated signal A transmission path estimation signal 518. Similarly, amodulated signal B transmission path estimation section 519 haspost-despreading received quadrature baseband signal 516 as input,estimates modulated signal B channel fluctuation (h22(t) in FIG. 2B)based on radio wave propagation environment estimation symbol 104contained in modulated signal B (FIG. 2A), and outputs the estimationresult as a modulated signal B transmission path estimation signal 520.

A frame synchronization section 521 has post-despreading receivedquadrature baseband signals 506 and 516 as input, forms a framesynchronization signal 522 for maintaining synchronization betweenframes based on predetermined symbols contained in received quadraturebaseband signals 506 and 516 and so forth, and outputs this framesynchronization signal 522.

A demodulation section 523 has modulated signal A transmission pathestimation signals 508 and 518, modulated signal B transmission pathestimation signals 510 and 520, post-despreading received quadraturebaseband signals 506 and 516, and frame synchronization signal 522 asinput, and by demodulating received quadrature baseband signals 506 and516 using transmission path estimation signals 508, 518, 510, and 520,and frame synchronization signal 522, obtains a modulated signal Areceived digital signal 524 and modulated signal B received digitalsignal 525, and outputs these signals.

FIG. 7 shows the detailed configuration of demodulation section 523.Demodulation section 523 has a modulated signal A and B demodulationsection 608 and a modulated signal B demodulation section 610.

Modulated signal A and B demodulation section 608 has modulated signal Atransmission path estimation signals 508 and 518, modulated signal Btransmission path estimation signals 510 and 520, post-despreadingreceived quadrature baseband signals 506 and 516, and framesynchronization signal 522 as input, and by demodulating receivedquadrature baseband signals 506 and 516 using transmission pathestimation signals 508, 518, 510, and 520, and frame synchronizationsignal 522, obtains a modulated signal A received digital signal 524 andmodulated signal B received digital signal 525-1, and outputs thesesignals.

In addition to modulated signal A transmission path estimation signals508 and 518, modulated signal B transmission path estimation signals 510and 520, post-despreading received quadrature baseband signals 506 and516, and frame synchronization signal 522, modulated signal Bdemodulation section 610 also has as input modulated signal A receiveddigital signal 524 obtained by modulated signal A and B demodulationsection 608, and using these, outputs a received digital signal 525-2for modulated signal B.

FIG. 8 shows another sample configuration of demodulation section 523.In FIG. 8, items that operate in the same way as in FIG. 7 are assignedthe same codes as in FIG. 7.

Modulated signal A and B demodulation section 608 has modulated signal Atransmission path estimation signals 508 and 518, modulated signal Btransmission path estimation signals 510 and 520, post-despreadingreceived quadrature baseband signals 506 and 516, and framesynchronization signal 522 as input, and by demodulating receivedquadrature baseband signals 506 and 516 using transmission pathestimation signals 508, 518, 510, and 520, and frame synchronizationsignal 522, obtains modulated signal A received digital signal 524, amodulated signal B received digital signal 525-1, a first soft decisionvalue signal 701, and a second soft decision value signal 702, andoutputs these signals.

A modulated signal B demodulation section 703 has first soft decisionvalue signal 701 and second soft decision value signal 702 as input,obtains received digital signal 525-2 by demodulating first softdecision value signal 701 and second soft decision value signal 702, andoutputs this received digital signal 525-2.

Next, the operation of this embodiment will be explained.

As described above, when transmitting apparatus 300 of this embodimenttransmits two modulated signals A and B from separate antennas, the samedata is transmitted a plurality of times, changing the mapping pattern(that is, the signal point arrangement mode), for modulated signal Aonly. Thus, to consider a comparison with use of space-time blockcoding, whereas the same information is transmitted repeatedly by aplurality of antennas in space-time block coding, transmitting apparatus300 transmits information repeatedly from only one antenna but does nottransmit the same information repeatedly from the other antenna, therebyenabling a higher data transmission speed to be maintained than whenspace-time block coding is used.

Also, by receiving such signals, receiving apparatus 500 can demodulatemodulated signal A and modulated signal B with good error rateperformances. This procedure will be described in detail below.

First, using radio wave propagation environment estimation symbols,receiving apparatus 500 estimates channel fluctuations h11(t), h12(t),h21(t), and h22(t) between the antennas of the modulated signals at timet. The relationship between received signal R1(i) received by antenna109 and received signal R2(i) received by antenna 110 at time i, andmodulated signal S1(i)transmitted from transmitting antenna 107 andmodulated signal S2(i) transmitted from transmitting antenna 108 at timei can be expressed by the following equation using h11(i), h12(i),h21(i), h22(i).

$\begin{matrix}{\begin{pmatrix}{R\; 1(i)} \\{R\; 2(i)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(i)} & {h\; 12(i)} \\{h\; 21(i)} & {h\; 22(i)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)} \\{S\; 2(i)}\end{pmatrix}}} & (1)\end{matrix}$

Similarly, the relationship in the following equation holds true at timei+1.

$\begin{matrix}{\begin{pmatrix}{R\; 1\left( {i + 1} \right)} \\{R\; 2\left( {i + 1} \right)}\end{pmatrix} = {\begin{pmatrix}{h\; 11\left( {i + 1} \right)} & {h\; 12\left( {i + 1} \right)} \\{h\; 21\left( {i + 1} \right)} & {h\; 22\left( {i + 1} \right)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)^{\prime}} \\{S\; 2\left( {i + 1} \right)}\end{pmatrix}}} & (2)\end{matrix}$

S1(i) and S2(i) can be obtained from the relationship in equation (1),and S1(i)′ and S2(i+1) can be obtained from the relationship in equation(2).

Here, if the difference between the time in which data symbols 102 and105 are transmitted and the time in which data symbols 103 and 106 aretransmitted is small, as in the example in FIG. 2A (in which there isonly a difference of time “1”), then h11(i)≈h11(i+1), h12(i)≈h12(i+1),h21(i)≈h21(i+1), and h22(i)≈h22(i+1). Therefore, in such a case, thematrices of equation (1) and equation (2) are almost equal matrices, butthe (S1(i), S2(i)) and (S1(i)′ S2(i+1)) vectors are different, andtherefore the likelihoods of the data obtained by demodulation aredifferent.

In particular, the difference in data likelihoods increases when theLikelihood Detection shown in. “A simple transmit diversity techniquefor wireless communications,” IEEE Journal on Select Areas inCommunications, pp. 1451-1458, vol. 16, no. 8, October 1998, is used.

An example of variation of candidate signal points in time i and timei+1 received signals at this time is shown in FIG. 52A and FIG. 52B.FIG. 52A shows a candidate signal point arrangement for a time ireceived signal, and FIG. 52B shows a candidate signal point arrangementfor a time i+1 received signal. Thus, in this embodiment the candidatesignal point arrangement differs for time i and time i+1, and thereforethe reception quality at time i and the reception quality at time i+1differ. By this means, a diversity effect can be obtained. FIG. 52A andFIG. 52B will be explained in detail later herein. Transmittingapparatus 300 and receiving apparatus 500 of this embodiment make use ofthis characteristic to improve receive data quality.

This will now be explained in specific terms. As described above,transmitting apparatus 300 forms modulated signal A (S1(i), S1(i)′) bymodulating the same transmit data so that the time i and time i+1 signalpoint arrangements vary, and transmits this at the same time asmodulated signal B (S2(i), S2(i+1)) using a different antenna. By thismeans, the receiving side separates and demodulates modulated signalS1(i) and modulated signal S2(i) from a signal in which modulated signalS1(i) and modulated signal S2(i) are multiplexed at time i, anddemodulates modulated signal S1(i)′ and modulated signal S2(i+1) from asignal in which modulated signal S1(i)′ and modulated signal S2(i+1) aremultiplexed at time i+1.

Here, since the modulated signal A signal point arrangement changesbetween time i and time i+1, the signal point arrangement of theabove-described time i multiplexed signal and the signal pointarrangement of the above-described time i+1 multiplexed signal alsodiffer, and as a result, the error rates of the receive data when theseare separated and modulated are also different.

When the time i reception quality is better, receiving apparatus 500 ofthis embodiment uses the signal obtained by demodulating modulatedsignal S1(i) as the modulated signal A demodulation result. That is tosay, the S1(i) demodulation result is also used as the modulated signalS1(i)′ demodulation result. Then modulated signal S2(i) whose receptionquality is good is demodulated by means of normal separation andmodulation from a signal in which modulated signal S1(i) and modulatedsignal S2(i) are multiplexed. In contrast, modulated signal S2(i+1)whose reception quality is poor is replaced by modulated signal S1(i)′whose reception quality is poor, and demodulation is performed using thedemodulation result of modulated signal S1(i) whose reception quality isgood.

On the other hand, when the time i+1 reception quality is better,receiving apparatus 500 uses the signal obtained by demodulatingmodulated signal S1(i)′ as the modulated signal A demodulation result.That is to say, the S1(i)′ demodulation result is also used as themodulated signal S1(i) demodulation result. Then modulated signalS2(i+1) whose reception quality is good is demodulated by means ofnormal separation and modulation from a signal in which modulated signalS1(i)′ and modulated signal S2(i+1) are multiplexed. In contrast,modulated signal S2(i) whose reception quality is poor is replaced bymodulated signal S1(i) whose reception quality is poor, and demodulationis performed using the demodulation result of modulated signal S1(i)′whose reception quality is good.

By using the modulated signal A demodulation result of a time whendemodulation precision is good in this way, the modulated signal Ademodulation error rate performances can be improved, and by performingmodulated signal B demodulation using the modulated signal Ademodulation result of a time when demodulation precision is good, themodulated signal B demodulation error rate performances can also beimproved.

The actual demodulation (decoding) procedure of receiving apparatus 500is as follows.

<1> Time i detection is performed, and (S1(i), S2(i)) is obtained.<2> Time i+1 detection is performed, and (S1(i)′, S2(i+1)) is obtained.<3> The time i and time i+1 reception qualities are compared.

If the time i reception quality is better, (S1(i), S2(i)) data obtainedin time i detection is used directly. Then S2(i+1) data is obtained byestimating S1(i)′ of time i+1 from S1(i) obtained in time i detection,and using that result.

On the other hand, if the time i+1 reception quality is better, (S1(i)′,S2(i+1)) data obtained in time i+1 detection is used directly. ThenS2(i) data is obtained by estimating S1(i) of time i from S1(i)′obtained in time i+1 detection, and using that result.

In receiving apparatus 500, modulated signal A received digital signal524 and modulated signal B received digital signal 525 are obtained byperforming this kind of demodulation processing in demodulation section523.

This demodulation processing will now be described in greater detail.

In the example in this embodiment, modulated signal A and modulatedsignal B are both QPSK modulated signals, and it is therefore possibleto transmit a total of 4 bits—2 bits in modulated signal A and 2 bits inmodulated signal B—at the same time. That is to say, it is possible totransmit 0000, 0001, . . . , 1111. It is assumed that the upper 2 bitsare the 2 bits transmitted in modulated signal A, and the lower 2 bitsare the 2 bits transmitted in modulated signal B.

The overall operation of demodulation section 523 will first beexplained.

First, at time i, demodulation section 523 finds signal points(candidate signal points) in the 16 signal point (0000, 0001, . . . ,1111) I-Q plane using modulated signal A transmission path estimationsignal 508 and modulated signal B transmission path estimation signal510. The appearance of these signal points is shown by reference codes1302 in FIG. 14. Also, demodulation section 523 has as input the signalof the signal point indicated by reference code 1301 in FIG. 14 asreceived quadrature baseband signal 506 from despreading section 505.Next, demodulation section 523 calculates, for example, the square ofthe distance from signal point 1301 in the I-Q plane for all the signalpoints indicated by reference code 1302 in FIG. 14. That is to say, thesquare of the distance between signal point 1302 of transmit bits 0000and signal point 1301 (X0000(i)) is found, and in the same way thesquares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (X0001(i), . . . , X1111(i))are found.

Similarly, at time i, demodulation section 523 finds signal points(candidate signal points) in the 16 signal point (0000, 0001, . . . ,1111) I-Q plane using modulated signal A transmission path estimationsignal 518 and modulated signal B transmission path estimation signal520. The appearance of these signal points is shown by reference codes1302 in FIG. 14. Also, demodulation section 523 inputs the signal of thesignal point indicated by reference code 1301 in FIG. 14 as receivedquadrature baseband signal 516 from despreading section 515. Next,demodulation section 523 calculates the square of the distance fromsignal point 1301 in the I-Q plane for all the signal points indicatedby reference code 1302 in FIG. 14. That is to say, the square of thedistance between signal point 1302 of transmit bits 0000 and signalpoint 1301 (Y0000(i) is found, and in the same way the squares of thedistances between signal points 1302 of transmit bits 0001, . . . , 1111and signal point 1301 (Y0001(i), . . . , Y1111(i)) are found.

Demodulation section 523 then finds the sum of X0000(i) and Y0000(i),Z0000(i)=X0000(i)+Y0000(i), and similarly finds Z0001(i), . . . ,Z1111(i). In the same way, demodulation section 523 finds Z0000(i+1),Z0001(i+1), . . . , Z1111(i+1) for time i+1. Next, demodulation section523 compares the likelihoods of time i and time i+1 receive data.

For example, demodulation section 523 searches for the smallest valueamong Z0000(i), Z0001(i), Z1111(i). Let that value be designated F(i).Then demodulation section 523 searches for the second-smallest value.Let that value be designated S(i).

Similarly, demodulation section 523 searches for the smallest valueamong Z0000(i+1), Z0001(i+1), . . . , Z1111(i+1). Let that value bedesignated F(i+1). Then demodulation section 523 searches for thesecond-smallest value. Let that value be designated S(i+1).

Then, for example, demodulation section 523 finds R(i)=F(i)/S(i), andR(i+1)=F(i+1)/S(i+1).

When R(i+1)>R(i), demodulation section 523 determines that the time ireception quality is better, and determines that the 4 bits providingF(i) are correct data. Then, as the 2 bits transmitted in modulatedsignal A, the 2 bits obtained at time i are taken as time i and time i+1receive data. For modulated signal B, as the 2 bits transmitted at timei, the 2 bits obtained at time i are taken directly as receive data,while the 2 bits transmitted at time i+1 are determined making use ofthe fact that the 2 bits transmitted in time i+1 modulated signal A havealready been determined. For example, if the 2 bits transmitted inmodulated signal A are 00, the 2 bits transmitted in modulated signal Bat time i+1 are determined by searching for the item with the smallestvalue among Z0000(i+1), Z0001(i+1), Z0010(i+1), and Z0011(i+1).Similarly, if the 2 bits transmitted in modulated signal A are 01, the 2bits transmitted in modulated signal B at time i+1 are determined bysearching for the item with the smallest value among Z0100(i+1),Z0101(i+1), Z0110(i+1), and Z0111(i+1). The 2 bits transmitted inmodulated signal B at time i+1 are also determined in the same way whenthe 2 bits transmitted in modulated signal A are 10 or 11.

When R(i)>R(i+1), demodulation section 523 determines that the time i+1reception quality is better, and determines that the 4 bits providingF(i+1) are correct data. Then, as the 2 bits transmitted in modulatedsignal A, the 2 bits obtained at time i+1 are taken as time i and timei+1 receive data. For modulated signal B, as the 2 bits transmitted attime i+1, the 2 bits obtained at time i+1 are taken directly as receivedata, while the 2 bits transmitted at time i are determined making useof the fact that the 2 bits transmitted in time i modulated signal Ahave already been determined. For example, if the 2 bits transmitted inmodulated signal A are 00, the 2 bits transmitted in modulated signal Bat time i are determined by searching for the item with the smallestvalue among Z0000(i), Z0001(i), Z0010(i), and Z0011(i). Similarly, ifthe 2 bits transmitted in modulated signal A are 01, the 2 bitstransmitted in modulated signal B at time i are determined by searchingfor the item with the smallest value among Z0100(i), Z0101(i), Z0110(i),and Z0111(i). The 2 bits transmitted in modulated signal B at time i arealso determined in the same way when the 2 bits transmitted in modulatedsignal A are 10 or 11.

The operation when demodulation section 523 is configured as shown inFIG. 7 and FIG. 8 will now be explained.

When demodulation section 523 is configured as shown in FIG. 7, asdescribed above, of the data transmitted in modulated signal A at time iand time i+1, modulated signal A and B demodulation section 608 outputsdata demodulated from the signal of the time with the better receptionquality as modulated signal A received digital signal 524. Also, asdescribed above, data transmitted in modulated signal B of a time ofgood reception quality is output as modulated signal B received digitalsignal 525-1.

As described above, modulated signal B demodulation section 610 hasmodulated signal A received digital signal 524 whose reception qualityis good as input, uses this to obtain received digital signal 525-2whose reception quality is good by demodulating modulated signal B of atime of poor reception quality, and outputs this received digital signal525-2.

When demodulation section 523 is configured as shown in FIG. 8, asdescribed above, of the data transmitted in modulated signal A at time iand time i+1, modulated signal A and B demodulation section 608 outputsdata demodulated from the signal of a time of good reception quality asmodulated signal A received digital signal 524. Also, modulated signal Aand B demodulation section 608 outputs Z0000(i), . . . , Z1111(i) asfirst soft decision value signal 701, and outputs Z0000(i+1), . . . ,Z1111(i+1) as second soft decision value signal 702. Furthermore,modulated signal A and B demodulation section 608 outputs receiveddigital signal 525-1 of modulated signal B of either time i or time i+1.

Modulated signal B demodulation section 703 has Z0000(i), . . . ,Z1111(i) comprising first soft decision value signal 701 and Z0000(i+1),. . . , Z1111(i+1) comprising second soft decision value signal 702 asinput, and, as described above, by performing modulated signal Bdemodulation based on the time i and time i+1 reception qualities,obtains modulated signal B received digital signal 525-2 of a differenttime from modulated signal B from which received digital signal 525-1was obtained, and outputs this received digital signal 525-2.

Thus, according to this embodiment, of modulated signals A and Btransmitted from different antennas, modulated signal A is formed bymodulating the same data a plurality of times while changing the signalpoint arrangement mode, and modulated signal B is formed not bymodulating the same data a plurality of times while changing the signalpoint arrangement mode but by performing sequential modulation of timeseries data (that is, by executing normal modulation), thereby enablingthe error rate performances of the data stream transmitted a pluralityof times to be improved, and as a result, the error rate performances ofboth streams (the two streams) to be improved, while maintaining ahigher data transmission speed than when space-time block coding isused.

Actually, on the receiving side, by taking the demodulation result ofmodulated signal A obtained based on a received signal of a time of goodreception quality as the modulated signal A received digital signal, andobtaining the received digital signal of modulated signal B received ata time of poor reception quality from a received signal of that time ofpoor reception quality using the already determined modulated signal Areceived digital signal of a time of good reception quality, the errorrate performances of modulated signal B received at a time of poorreception quality can also be improved.

Furthermore, when QPSK is used as the modulation method, if QPSKmodulated signals that have a mutual 45 o phase difference are formedfrom the same data for modulated signal A and transmitted, it ispossible to obtain a state in which the minimum Euclidian distance islarge at time i and time i+1, enabling error rate performances to besignificantly improved.

(1-1) Variant Example 1

In the above example, a case has been described in which the frameconfigurations transmitted by transmitting apparatus 300 are as shown inFIG. 2A, but the transmitted frame configurations may also be as shownin FIG. 9. The difference between the frame configurations in FIG. 9 andthe frame configurations in FIG. 2A is that the time difference intransmitting signal S1(i) in which the same data is modulated inmodulated signal A is made small in the case of FIG. 2A, but is madevery large in FIG. 9.

Consequently, the radio wave propagation environment is totallydifferent at time i and time j. Considering this, in the case of FIG. 9,the signal point arrangement of modulated signal A transmitted at time jis made the same as the signal point arrangement of modulated signal Atransmitted at time i. This is because it was considered that, even ifthe signal point arrangement of modulated signal A is not intentionallyvaried, the time i and time j reception qualities will differ to someextent due to differences in the radio wave propagation environment.

As a result, if the demodulation result of modulated signal A obtainedbased on a received signal of a time of good reception quality is takenas the modulated signal A received digital signal, and the receiveddigital signal of modulated signal B received at a time of poorreception quality from a received signal of that time of poor receptionquality is obtained using the already determined modulated signal Areceived digital signal of a time of good reception quality, the errorrate performances of modulated signal B received at a time of poorreception quality can also be improved in the same way as when signalswith the frame configurations shown in FIG. 2A are transmitted.

This will now be explained in specific terms. Equation (1) given aboveholds true at time i. Similarly, the relationship in the followingequation holds true at time j.

$\begin{matrix}{\begin{pmatrix}{R\; 1(j)} \\{R\; 2(j)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(j)} & {h\; 12(j)} \\{h\; 21(j)} & {h\; 22(j)}\end{pmatrix}\begin{pmatrix}{S\; 1(j)} \\{S\; 2(j)}\end{pmatrix}}} & (3)\end{matrix}$

In receiving apparatus 500, h11(j), h12(j), h21(j), and h22(j) inequation (3) are estimated using, for example, radio wave propagationenvironment estimation symbols 801 and 803 in FIG. 9. Here, since theradio wave propagation environment differs for time i and time j,h11(i)≠h11(j), h12(i)≠h12(j), h21(i)≠h21(j), and h22(i)≠h22(j).Therefore, time i and time j reception qualities are totally different.

A description will now be given of signal point arrangements in the I-Qplane for time i and time j taking the above into consideration.

Examples of modulated signal A signal point arrangements in the I-Qplane are shown in FIG. 3A through FIG. 3C. When the frameconfigurations shown in FIG. 9 are used, the time i and time j signalpoint arrangements may both be as shown in FIG. 3A, or may differ, withthe time i signal point arrangement as shown in FIG. 3A and the time jsignal point arrangement as shown in FIG. 3B. This is because, unlike inthe case of the frame configurations in FIG. 2A, the radio wavepropagation environment differs for time i and time j, and thereforeeven if the signal point arrangement is not intentionally varied at timei and time j, the reception quality is different for time i and time j.

The decoding procedure is described in detail below. This can beconsidered as similar to the operation in the case of the frameconfigurations in FIG. 2A. That is to say, time i+1 operations can bethought of as being replaced by time j operations.

<1> Time i detection is performed, and (S1(i), S2(i)) is obtained.<2> Time j detection is performed, and (S1(i), S2(j)) is obtained.<3> The time i and time j reception qualities are compared.If the time i reception quality is better, (S1(i) S2(i)) data obtainedin time i detection is used directly. Then S2(j) data is obtained byestimating S1(i) of time j from S1(i) obtained in time i detection, andusing that result.On the other hand, if the time j reception quality is better, (S1(i),S2(j)) data obtained in time j detection is used directly. Then S2(i)data is obtained by estimating S1(i) of time i from S1(i) obtained intime j detection, and using that result.

In receiving apparatus 500, modulated signal A received digital signal524 and modulated signal B received digital signal 525 are obtained byperforming this kind of demodulation processing in demodulation section523.

A description of the detailed operation of demodulation section 523 whentransmit signals with the frame configurations in FIG. 9 are receivedwill be omitted, as it is the same as described above with “time j”substituted for “time i+1” operations. However, a difference in abovetime i+1 and time j processing is that, whereas for time i+1, time i+1data likelihood is determined based on signal points (candidate signalpoints) obtained using radio wave propagation environment estimationsymbols 101 and 104 in FIG. 2A, for time j, time j data likelihood isdetermined based on signal points (candidate signal points) obtainedusing radio wave propagation environment estimation symbols 801 and 803in FIG. 9.

(1-2) Variant Example 2

Here, frame configurations transmitted by transmitting apparatus 300will be described for cases as shown in FIG. 10A and FIG. 10B.

With regard to the frame configurations shown in FIG. 10A, whereas withthe frame configurations in FIG. 2A the same data is transmitted twicein succession in modulated signal A, changing the signal pointarrangement mode, in the case of the frame configurations in FIG. 10Athe same data is transmitted three times in succession in modulatedsignal A, changing the signal point arrangement mode.

Also, with regard to the frame configurations shown in FIG. 10B, whereaswith the frame configurations in FIG. 9 the same data is transmittedtwice in succession in modulated signal A at separated times withoutchanging the signal point arrangement mode, in the case of the frameconfigurations in FIG. 10B the same data is transmitted three times insuccession in modulated signal A at separated times without changing thesignal point arrangement mode.

First, a case in which the frame configurations in FIG. 10A are usedwill be described.

The situation regarding the time i and time i+1 states is the same as inthe description relating to the frame configurations in FIG. 2A. Therelationship in the following equation holds true at time i+2.

$\begin{matrix}{\begin{pmatrix}{R\; 1\left( {i + 2} \right)} \\{R\; 2\left( {i + 2} \right)}\end{pmatrix} = {\begin{pmatrix}{h\; 11\left( {i + 2} \right)} & {h\; 12\left( {i + 2} \right)} \\{h\; 21\left( {i + 2} \right)} & {h\; 22\left( {i + 2} \right)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)^{''}} \\{S\; 2\left( {i + 2} \right)}\end{pmatrix}}} & (4)\end{matrix}$

As the time from time i to time i+2 is short, h11(i)≈h11(i+1)≈h11(i+2),h12(i)≈h12(i+1)≈h12(i+2), h21(i)≈h21(i+1)≈h21(i+2), andh22(i)≈h22(i+1)≈h22(i+2).

S1(i) and S2(i) can be obtained from the relationship in equation (1),S1(i)′ and S2(i+1) can be obtained from the relationship in equation(2), and S1(i)″ and S2(i+2) can be obtained from the relationship inequation (4).

At this time, the matrices of equation (1), equation (2), and equation(4) are almost equal matrices, but since the S1(i), S1(i)′, and S1(i)″signal points are changed, the (S1(i), S2(i)), (S1(i)′, S2(i+1)), and(S1(i)″, S2(i+2)) vectors are different, and therefore the likelihoodsof the data obtained in each of times i through i+2 are different. Atthis time, for example, the signal point arrangement in FIG. 11A may beused for S1(i) of time i, the signal point arrangement in FIG. 11B forS1(i)′ of time i+1, and the signal point arrangement in FIG. 11C forS1(i)″ of time i+2. By making the signal point arrangement modes formodulated signals S1(i), S1(i)′, and S1(i)″ with identical datadifferent in this way, the likelihoods of data obtained in each of timesi through i+2 can be changed efficiently.

Transmit signals with the frame configurations in FIG. 10A can be formedby transmitting apparatus 300 with the configuration shown in FIG. 4.Modulation section 304 need only have a configuration in which a mappingsection Z (not shown) is added to the configuration of modulationsection 304 in FIG. 5. Time i+2 mapping can then be performed by theadded mapping section Z.

The actual demodulation (decoding) procedure of receiving apparatus 500when signals with the frame configurations in FIG. 10A are received isas follows.

<1> Time i detection is performed, and (S1(i), S2(i)) is obtained.<2> Time i+1 detection is performed, and (S1(i)′, S2(i+1)) is obtained.<3> Time i+2 detection is performed, and (S1(i)″, S2(i+2)) is obtained.<4> The time i, time i+1, and time i+2 reception qualities are compared.

If, among time i, time i+1, and time i+2, the time i reception qualityis the best, (S1(i), S2(i)) data obtained in time i detection is useddirectly. Then S2(i+1) data is obtained by estimating S1(i)′ of time i+1from S1(i) obtained in time i detection, and using that result. Also,S2(i+2) data is obtained by estimating S1(i)″ of time i+2 from S1(i)obtained in time i detection, and using that result.

If the time i+1 reception quality is the best, (S1(i)′, S2(i+1)) dataobtained in time i+1 detection is used directly. Then S2(i) data isobtained by estimating S1(i) of time i from S1(i)′ obtained in time i+1detection, and using that result. Also, S2(i+2) data is obtained byestimating S1(i)″ of time i+2 from S1(i)′ obtained in time i+1detection, and using that result.

If the time i+2 reception quality is the best, (S1(i)″, S2(i+2)) dataobtained in time i+2 detection is used directly. Then S2(i) data isobtained by estimating S1(i) of time i from S1(i)″ obtained in time i+2detection, and using that result. Also, S2(i+1) data is obtained byestimating S1(i)′ of time i+1 from S1(i)″ obtained in time i+2detection, and using that result.

In receiving apparatus 500, modulated signal A received digital signal524 and modulated signal B received digital signal 525 are obtained byperforming this kind of demodulation processing in demodulation section523.

This demodulation processing will now be described in greater detail.

When modulated signal A and modulated signal B are both QPSK modulatedsignals, it is possible to transmit a total of 4 bits—2 bits inmodulated signal A and 2 bits in modulated signal B—at the same time.That is to say, it is possible to transmit 0000, 0001, 1111. It isassumed that the upper 2 bits are the 2 bits transmitted in modulatedsignal A, and the lower 2 bits are the 2 bits transmitted in modulatedsignal B.

The overall operation of demodulation section 523 will first beexplained.

First, at time i in FIG. 10A, demodulation section 523 finds signalpoints (candidate signal points) in the 16 signal point (0000, 0001, . .. , 1111) I-Q plane using modulated signal A transmission pathestimation signal 508 and modulated signal B transmission pathestimation signal 510. The appearance of these signal points is shown byreference codes 1302 in FIG. 14. Also, demodulation section 523 has asinput the signal of the signal point indicated by reference code 1301 inFIG. 14 as received quadrature baseband signal 506 from despreadingsection 505. Next, demodulation section 523 calculates, for example, thesquare of the distance from signal point 1301 in the I-Q plane for allthe signal points indicated by reference code 1302 in FIG. 14. That isto say, the square of the distance between signal point 1302 of transmitbits 0000 and signal point 1301 (X0000(i)) is found, and in the same waythe squares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (X0001(i), . . . , X1111(i))are found.

Similarly, at time i in FIG. 10A, demodulation section 523 finds signalpoints (candidate signal points) in the 16 signal point (0000, 0001, . .. , 1111) I-Q plane using modulated signal A transmission pathestimation signal 518 and modulated signal B transmission pathestimation signal 520. The appearance of these signal points is shown byreference codes 1302 in FIG. 14. Also, demodulation section 523 has asinput the signal of the signal point indicated by reference code 1301 inFIG. 14 as received quadrature baseband signal 516 from despreadingsection 515. Next, demodulation section 523 calculates the square of thedistance from signal point 1301 in the I-Q plane for all the signalpoints indicated by reference code 1302 in FIG. 14. That is to say, thesquare of the distance between signal point 1302 of transmit bits 0000and signal point 1301 (Y0000(i)) is found, and in the same way thesquares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (Y0001(i), . . . , Y1111(i))are found.

Demodulation section 523 then finds the sum of X0000(i) and Y0000(i),Z0000(i)=X0000(i)+Y0000(i), and similarly finds Z0001(i), . . . ,Z1111(i). In the same way, demodulation section 523 finds Z0000(i+1),Z0001(i+1), . . . , Z1111(i+1) for time i+1, and finds Z0000(i+2),Z0001(i+2), . . . , Z1111(i+2) for time i+2.

Next, demodulation section 523 compares the likelihoods of time i, timei+1, and time i+2 receive data.

For example, demodulation section 523 searches for the smallest valueamong Z0000(i), Z0001(i), . . . , Z1111(i). Let that value be designatedF(i). Then demodulation section 523 searches for the second-smallestvalue. Let that value be designated S(i).

Similarly, demodulation section 523 searches for the smallest valueamong Z0000(i+1), Z0001(i+1), . . . , Z1111(i+1). Let that value bedesignated F(i+1). Then demodulation section 523 searches for thesecond-smallest value. Let that value be designated S(i+1).

Similarly, demodulation section 523 searches for the smallest valueamong Z0000(i+2), Z0001(i+2), . . . , Z1111(i+2). Let that value bedesignated F(i+2). Then demodulation section 523 searches for thesecond-smallest value. Let that value be designated S(i+2).

Then, for example, demodulation section 523 finds R(i)=F(i)/S(i),R(i+1)=F(i+1)/S(i+1), and R(i+2)=F(i+2)/S(i+2). The time i, time i+1,and time i+2 reception qualities are estimated using the above values.

If the time i reception quality is determined to be the best, as the 2bits transmitted in modulated signal A, the 2 bits obtained at time iare taken as time i, time i+1, and time i+2 receive data. For modulatedsignal B, as the 2 bits transmitted at time i, the 2 bits obtained attime i are taken directly as receive data, while the 2 bits transmittedat times i+1 and i+2 are determined making use of the fact that the 2bits transmitted in time i+1 and i+2 modulated signal A have alreadybeen determined. If the time i+1 reception quality is determined to bethe best, as the 2 bits transmitted in modulated signal A, the 2 bitsobtained at time i+1 are taken as time i, time i+1, and time i+2 receivedata. For modulated signal B, as the 2 bits transmitted at time i+1, the2 bits obtained at time i+1 are taken directly as receive data, whilethe 2 bits transmitted at times i and i+2 are determined making use ofthe fact that the 2 bits transmitted in time i and i+2 modulated signalA have already been determined.

If the time i+2 reception quality is determined to be the best, as the 2bits transmitted in modulated signal A, the 2 bits obtained at time i+2are taken as time i, time i+1, and time i+2 receive data. For modulatedsignal B, as the 2 bits transmitted at time i+2, the 2 bits obtained attime i+2 are taken directly as receive data, while the 2 bitstransmitted at times i and i+1 are determined making use of the factthat the 2 bits transmitted in time i and i+1 modulated signal A havealready been determined.

An example of the detailed configuration of demodulation section 523 forperforming this kind of processing is shown in FIG. 12. As describedabove, of the data transmitted in modulated signal A at time i, timei+1, and time i+2, modulated signal A and B demodulation section 608outputs data demodulated from the signal of the time with the bestreception quality as modulated signal A received digital signal 524.Also, modulated signal A and B demodulation section 608 outputsZ0000(i), . . . , Z1111(i) as first soft decision value signal 701,Z0000(i+1), . . . , Z1111(i+1) as second soft decision value signal 702,and Z0000(i+2), . . . , Z1111(i+2) as a third soft decision value signal1101. Furthermore, modulated signal A and B demodulation section 608outputs received digital signal 525-1 of modulated signal B of one oftime i, time i+1, or time i+2.

Modulated signal B demodulation section 703 has Z0000(i), . . . ,Z1111(i) comprising first soft decision value signal 701, Z0000(i+1), .. . , Z1111(i+1) comprising second soft decision value signal 702, andZ0000(i+2), . . . , Z1111(i+2) comprising third soft decision valuesignal 1101, as input, and, as described above, by performing modulatedsignal B demodulation based on the time i, time i+1 and time i+2reception qualities, obtains modulated signal B received digital signal525-2 of a different time from modulated signal B from which receiveddigital signal 525-1 was obtained, and outputs this received digitalsignal 525-2.

When frame configurations such as shown in FIG. 10A are used in thisway, a time in which reception quality is best can be selected fromamong more times than when frame configurations such as shown in FIG. 2Aare used, enabling modulated signal A and B demodulated data withsignificantly better error rate performances to be obtained.

A case has been described here in which, as shown in FIG. 10A, the samedata is transmitted by three consecutive symbols, S1(i), S1(i)′, andS1(i)″, changing the signal point arrangement, but this is not alimitation, and essentially it is only necessary that, when a modulatedsignal with the same data is transmitted a plurality of times at shorttime intervals, the reception quality of each time be varied by changingthe signal point arrangement of modulated signals with the same data.That is to say, modulated signals transmitted at times i, i+1, and i+2may be transmitted at times i, i+n, and i+m. At this time, it iseffective if the following relationships hold true:h11(i)≈h11(i+n)≈h11(i+m), h12(i)≈h12(i+n)≈h12(i+m),h21(i)≈h21(i+n)≈h21(i+m), and h22(i)≈h22(i+n)≈h22(i+m). In this case,operations can be executed in the same way as described above,considering an above-described time i+1 operation as a time i+noperation, and an above-described time i+2 operation as a time i+moperation.

Next, a case in which the frame configurations in FIG. 10B are used willbe described.

As stated above, with regard to the frame configurations shown in FIG.10B, whereas with the frame configurations in FIG. 9 the same data istransmitted twice in succession in modulated signal A at separated timeswithout changing the signal point arrangement, in the case of the frameconfigurations in FIG. 10B the same data is transmitted three times insuccession in modulated signal A at separated times without changing thesignal point arrangement.

The situation regarding the time i and j states is the same as in thedescription relating to the frame configurations in FIG. 9. Therelationship in the following equation holds true at time k.

$\begin{matrix}{\begin{pmatrix}{R\; 1(k)} \\{R\; 2(k)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(k)} & {h\; 12(k)} \\{h\; 21(k)} & {h\; 22(k)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)^{''}} \\{S\; 2(k)}\end{pmatrix}}} & (5)\end{matrix}$

Here, times i, j, and k are times for which the radio wave propagationenvironment differs, and therefore h11(i)≠h11(j)≠h11(k),h12(i)≠h12(j)≠h12(k), h21(i)≠h21(j)≠h21(k), and h22(i)≠h22(j)≠h22(k).Therefore, times i, j, and k reception qualities are totally different.Considering this, in the case of FIG. 10B, the signal point arrangementof modulated signal A transmitted at time j and time k is made the sameas the signal point arrangement of modulated signal A transmitted attime i. This is because it was considered that, even if the signal pointarrangement of modulated signal A is not intentionally varied, the timei, time j, and time k reception qualities will differ to some extent dueto differences in the radio wave propagation environment.

Examples of modulated signal A signal point arrangements in the I-Qplane are shown in FIG. 11A through FIG. 11C. When the frameconfigurations shown in FIG. 108 are used, the times i, j, and k signalpoint arrangements may all be as shown in FIG. 11A, or may differ, withthe time i signal point arrangement as shown in FIG. 11A, the time jsignal point arrangement as shown in FIG. 11B, and the time k signalpoint arrangement as shown in FIG. 11C. This is because the radio wavepropagation environment differs for times i, j, and k, and thereforeeven if the signal point arrangement is not intentionally varied in eachtime, the reception quality is different for each time.

The actual demodulation (decoding) procedure of receiving apparatus 500when signals with the frame configurations in FIG. 10B are received isas follows.

<1> Time i detection is performed, and (S1(i), S2(i)) is obtained.<2> Time j detection is performed, and (S1(i), S2(j)) is obtained.<3> Time k detection is performed, and (S1(i), S2(k)) is obtained.<4> The time i, time j, and time k reception qualities are compared.

If, among time i, time j, and time k, the time i reception quality isthe best, (S1(i), S2(i)) data obtained in time i detection is useddirectly. Then S2(j) data is obtained by estimating S1(i) of time j fromS1(i) obtained in time i detection, and using that result. Also, S2(k)data is obtained by estimating S1(i) of time k from S1(i) obtained intime i detection, and using that result.

If the time j reception quality is the best, (S1(i), S2(j)) dataobtained in time j detection is used directly. Then S2(i) data isobtained by estimating S1(i) of time i from S1(i) obtained in time jdetection, and using that result. Also, S2(k) data is obtained byestimating S1(i) of time k from S1(i) obtained in time j detection, andusing that result.

If the time k reception quality is the best, (S1(i), S2(k)) dataobtained in time k detection is used directly. Then S2(i) data isobtained by estimating S1(i) of time i from S1(i) obtained in time kdetection, and using that result. Also, S2(j) data is obtained byestimating S1(i) of time j from S1(i) obtained in time k detection, andusing that result.

In receiving apparatus 500, modulated signal A received digital signal524 and modulated signal B received digital signal 525 are obtained byperforming this kind of demodulation processing in demodulation section523.

This demodulation processing will now be described in greater detail.

When modulated signal A and modulated signal B are both QPSK modulatedsignals, it is possible to transmit a total of 4 bits—2 bits inmodulated signal A and 2 bits in modulated signal B—at the same time.That is to say, it is possible to transmit 0000, 0001, . . . , 1111. Itis assumed that the upper 2 bits are the 2 bits transmitted in modulatedsignal A, and the lower 2 bits are the 2 bits transmitted in modulatedsignal B.

The overall operation of demodulation section 523 will first beexplained.

First, at time i in FIG. 10B, demodulation section 523 finds signalpoints (candidate signal points) in the 16 signal point (0000, 0001, . .. , 1111) I-Q plane using modulated signal A transmission pathestimation signal 508 and modulated signal B transmission pathestimation signal 510. The appearance of these signal points is shown byreference codes 1302 in FIG. 14. Also, demodulation section 523 has asinput the signal of the signal point indicated by reference code 1301 inFIG. 14 as received quadrature baseband signal 506 from despreadingsection 505. Next, demodulation section 523 calculates, for example, thesquare of the distance from signal point 1301 in the I-Q plane for allthe signal points indicated by reference code 1302 in FIG. 14. That isto say, the square of the distance between signal point 1302 of transmitbits 0000 and signal point 1301 (X0000(i)) is found, and in the same waythe squares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (X0001(i), . . . , X1111(i))are found.

Similarly, at time i in FIG. 10B, demodulation section 523 finds signalpoints (candidate signal points) in the 16 signal point (0000, 0001, . .. , 1111) I-Q plane using modulated signal A transmission pathestimation signal 518 and modulated signal B transmission pathestimation signal 520. The appearance of these signal points is shown byreference codes 1302 in FIG. 14. Also, demodulation section 523 has asinput the signal of the signal point indicated by reference code 1301 inFIG. 14 as received quadrature baseband signal 516 from despreadingsection 515. Next, demodulation section 523 calculates the square of thedistance from signal point 1301 in the I-Q plane for all the signalpoints indicated by reference code 1302 in FIG. 14. That is to say, thesquare of the distance between signal point 1302 of transmit bits 0000and signal point 1301 (Y0000(i)) is found, and in the same way thesquares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (Y0001(i), . . . , Y1111(i))are found.

Demodulation section 523 then finds the sum of X0000(i) and Y0000(i),Z0000(i)=X0000(i) Y0000(i), and similarly finds Z0001(i), . . . ,Z1111(i). In the same way, demodulation section 523 finds Z0000(j),Z0001(j), . . . , Z1111(j) for time j, and finds Z0000(k), Z0001 (k), .. . , Z1111(k) for time k.

Next, demodulation section 523 compares the likelihoods of time i, timej, and time k receive data.

For example, demodulation section 523 searches for the smallest valueamong Z0000(i), Z0001(i), . . . , Z1111(i). Let that value be designatedF(i). Then demodulation section 523 searches for the second-smallestvalue. Let that value be designated S(i).

Similarly, demodulation section 523 searches for the smallest valueamong Z0000(j), Z0001(j), . . . , Z1111(j). Let that value be designatedF(j). Then demodulation section 523 searches for the second-smallestvalue. Let that value be designated S(j).

Similarly, demodulation section 523 searches for the smallest valueamong Z0000(k), Z0001(k), . . . , Z1111(k). Let that value be designatedF(k). Then demodulation section 523 searches for the second-smallestvalue. Let that value be designated S(k).

Then, for example, demodulation section 523 finds R(i)=F(i)/S(i),R(j)=F(j)/S(j), and R(k)=F(k)/S(k). The time i, time j, and time kreception qualities are estimated using the above values.

If the time i reception quality is determined to be the best, as the 2bits transmitted in modulated signal A, the 2 bits obtained at time iare taken as time i, time j, and time k receive data. For modulatedsignal B, as the 2 bits transmitted at time i, the 2 bits obtained attime i are taken directly as receive data, while the 2 bits transmittedat times j and k are determined making use of the fact that the 2 bitstransmitted at time j and k modulated signal A have already beendetermined.

If the time j reception quality is determined to be the best, as the 2bits transmitted in modulated signal A, the 2 bits obtained at time jare taken as time i, time j, and time k receive data. For modulatedsignal B, as the 2 bits transmitted at time j, the 2 bits obtained attime j are taken directly as receive data, while the 2 bits transmittedat times i and k are determined making use of the fact that the 2 bitstransmitted at time i and k modulated signal A have already beendetermined.

If the time k reception quality is determined to be the best, as the 2bits transmitted in modulated signal A, the 2 bits obtained at time kare taken as time i, time j, and time k receive data. For modulatedsignal B, as the 2 bits transmitted at time k, the 2 bits obtained attime k are taken directly as receive data, while the 2 bits transmittedat times i and j are determined making use of the fact that the 2 bitstransmitted at time i and j modulated signal A have already beendetermined.An example of the detailed configuration of demodulation section 523 forperforming this kind of processing is shown in FIG. 12. As describedabove, of the data transmitted in modulated signal A at time i, time j,and time k, modulated signal A and B demodulation section 608 outputsdata demodulated from the signal of the time with the best receptionquality as modulated signal A received digital signal 524. Also,modulated signal A and B demodulation section 608 outputs Z0000(i), . .. , Z1111(i) as first soft decision value signal 701, Z0000(j), . . . ,Z1111(j) as second soft decision value signal 702, and Z0000(k), . . . ,Z1111(k) as third soft decision value signal 1101. Furthermore,modulated signal A and B demodulation section 608 outputs receiveddigital signal 525-1 of modulated signal B of one of time i, time j, ortime k.

Modulated signal B demodulation section 703 has Z0000(i), . . . ,Z1111(i) comprising first soft decision value signal 701, Z0000(j), . .. , Z1111(j) comprising second soft decision value signal 702, andZ0000(k), . . . , Z1111(k) comprising third soft decision value signal1101, as input, and, as described above, by performing modulated signalB demodulation based on the time i, time j, and time k receptionqualities, obtains modulated signal B received digital signal 525-2 of adifferent time from modulated signal B from which received digitalsignal 525-1 was obtained, and outputs this received digital signal525-2.

When frame configurations such as shown in FIG. 10B are used in thisway, a time in which reception quality is best can be selected fromamong more times than when frame configurations such as shown in FIG. 9are used, enabling modulated signal A and B demodulated data withsignificantly better error rate performances to be obtained.

(1-3) Variant Example 3

Here, an example will be described in which the frame configurationstransmitted by transmitting apparatus 300 are as shown in FIG. 13instead of FIG. 2A.

The difference between the frame configurations in FIG. 13 and the frameconfigurations in FIG. 2A is that the time difference in transmittingsignal S1(i) and S1(i)′ in which the same data is modulated in modulatedsignal A is “1” in the case of FIG. 2A, but is “n” in FIG. 13.

Here, if n is such that the relationships h11(i)≈h11(i+n),h12(i)≈h12(i+n), h21(i)≈h21(i+n), and h22(i)≈h22(i+n) hold true,operations can be executed in the same way as when signals with theframe configurations in FIG. 2A are transmitted. That is to say,operations can be executed in the same way, considering anabove-described time i+1 operation as a time i+n operation.

(1-4) Variant Example 4

Here, it is proposed that the transmission power of modulated signal Aor the transmission power of modulated signal B be made to differbetween time i and time i+1. By so doing, the reception quality can bechanged for time i and time i+1, in the same way as when the modulatedsignal A signal point arrangement pattern is changed for time i and timei+1 as described above, enabling the same kind of effect to be obtainedas when the above-described frame configurations are used. Furthermore,when the above-described frame configurations are combined, thedifference in reception quality of each time can be made significantlygreater. That is to say, changing the signal point arrangement mode istaken to include changing the transmission power.

Specifically, modulated signals S1(i) and S2(i) for which equation (1)holds true are transmitted at time i, and modulated signals rS1(i)′ andS2(i+1) or modulated signals S1(i)′ and rS2(i+1) for which equation (6)or equation (7) below holds true are transmitted at time i+1.

$\begin{matrix}{\begin{pmatrix}{R\; 1\left( {i + 1} \right)} \\{R\; 2\left( {i + 1} \right)}\end{pmatrix} = {\begin{pmatrix}{h\; 11\left( {i + 1} \right)} & {h\; 12\left( {i + 1} \right)} \\{h\; 21\left( {i + 1} \right)} & {h\; 22\left( {i + 1} \right)}\end{pmatrix}\begin{pmatrix}{{rS}\; 1(i)^{\prime}} \\{S\; 2\left( {i + 1} \right)}\end{pmatrix}}} & (6) \\{\begin{pmatrix}{R\; 1\left( {i + 1} \right)} \\{R\; 2\left( {i + 1} \right)}\end{pmatrix} = {\begin{pmatrix}{h\; 11\left( {i + 1} \right)} & {h\; 12\left( {i + 1} \right)} \\{h\; 21\left( {i + 1} \right)} & {h\; 22\left( {i + 1} \right)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)^{\prime}} \\{{rS}\; 2\left( {i + 1} \right)}\end{pmatrix}}} & (7)\end{matrix}$

The difference between equation (6) and equation (7) lies in whether thetransmission power of modulated signal A (S1) is changed or thetransmission power of modulated signal B (S2) is changed. Changing thereception quality by changing the transmission power in this way can beimplemented in combination with the embodiment below.

(1-5) Variant Example 5

The configuration of the transmitting apparatus is not limited to theconfiguration in FIG. 4, and the configuration of modulation section 304is not limited to the configuration in FIG. 5. The essential elementsare that a first modulation section and second modulation section isprovided, a first modulated signal is formed by the first modulationsection by modulating the same data of first transmit data a pluralityof times while changing the signal point arrangement mode or leaving atime interval of a plurality of symbols, a second modulated signal isformed by time series modulation of second transmit data, and thesefirst and second modulated signals are transmitted from differentantennas.

The configuration of the receiving apparatus is not limited to theconfiguration in FIG. 6, and configurations of demodulation section 523are not limited to the configurations in FIG. 6, FIG. 7, and FIG. 8. Theessential elements are that the demodulation result of modulated signalA (that is, a modulated signal transmitted with the same data modulateda plurality of times) obtained based on a received signal of a time ofgood reception quality is taken as the modulated signal A receiveddigital signal, and using the already determined received digital signalof modulated signal A of a time of good reception quality, a receiveddigital signal of modulated signal B transmitted at a time of poorreception quality from a received signal of that time of poor receptionquality is obtained.

For each antenna, a single antenna may be composed of a plurality ofantennas. Also, in the above embodiment, a case has been described inwhich the number of modulated signals and the number of antennas are thesame, but more antennas than the number of modulated signals n (n≧2) maybe provided, and the transmitting antennas may be switched in use. Ifthis is done, the reception qualities of each time can be made to differstill more by switching the transmitting antennas. This also applies inthe case of embodiments described later herein.

In the above embodiment, a case has been described in which, forexample, R(i)=F(i)/S(i), R(i+1)=F(i+1)/S(i+1), R(i+2)=F(i+2)/S(i+2),R(j)=F(j)/S(j), and R(k)=F(k)/S(k) are used as formulas for findingreception quality, but this is not a limitation, and reception qualitycan also similarly be found using, for example, formulas R(i)=F(i)−S(i),R(i+1)=F(i+1)−S(i+1), R(i+2)=F(i+2)−S(i+2), R(j)=F(j)−S(j), andR(k)=F(k)−S(k). This also applies to embodiments described later herein.However, when such formulas are used, size relationships are theopposite of those described in the embodiment. That is to say, receptionquality is better for a larger value of R(i).

In the above embodiment, a frame configuration whereby the same data istransmitted twice in modulated signal A and a frame configurationwhereby the same data is transmitted three times in modulated signal Ahave been proposed, but frame configurations are not limited to these,and the present invention can also be similarly implemented with a frameconfiguration whereby the same data is transmitted n (n≧4) times inmodulated signal A. Here, as the value of n increases, the apparent datatransmission speed at which transmission is possible with modulatedsignal A declines, but error rate performances when modulated signals Aand B are demodulated improve, and therefore making n larger the poorerthe radio wave propagation environment enables the effective datatransmission speed to be increased.

In the above embodiment, a case in which a spread spectrum system isused has been described as an example, but this is not a limitation, andthe present invention can also be similarly implemented with asingle-carrier system in which spectral diffusion is not performed. Atthis time, the spreading section can be omitted from the transmittingapparatus configuration, and the despreading section can be omitted fromthe receiving apparatus configuration. The coding of this implementationcan also be executed in each carrier in a multicarrier system, taking anOFDM system as an example. When an OFDM system is used, for example, thetransmitting apparatus would have a configuration in which an inverseFourier transform section is added in order to generate a modulatedsignal using OFDM, and the receiving apparatus would have aconfiguration in which a Fourier transform section is added. This alsoapplies to embodiments described later herein.

In the above embodiment, coding of modulated signal A and modulatedsignal B is performed with respect to the time axis direction. That isto say, in the examples in the above-described embodiment, modulatedsignals of the same data are transmitted at different times in modulatedsignal A. However, the coding (arrangement in modulated signal transmitframes) of this embodiment can be performed in the frequency axisdirection, especially when using a multicarrier system of which OFDM isan example. That is to say, modulated signal A could have a plurality ofidentical data symbols placed on different carriers.

In the above embodiment, improving the reception quality (error rateperformances) of modulated signal A also improves the reception quality(error rate performances) of modulated signal B. If, in addition to theabove embodiment, block coding, convolutional coding such as Viterbicoding or turbo coding, or coding such as LDPC (Low-DensityParity-Check) coding, is executed on modulated signal A, the receptionquality of modulated signal A can be further improved, enabling thereception quality of modulated signal B also to be further improved.This also applies to embodiments described later herein.

Block coding, convolutional coding such as Viterbi coding or turbocoding, and error correction coding such as LDPC coding, are not limitedto execution on modulated signal A only, but may be executed for bothmodulated signals A and B. In this case, modulated signal B isdemodulated after demodulation of modulated signal A.

In the above embodiment, a configuration whereby two modulated signalsare transmitted from two antennas has been described as an example, butthe present invention is not limited to this, and the same data may betransmitted in at least one modulated signal of n modulated signals aplurality of times using different times or different frequencies. Thisalso applies to embodiments described later herein.

(2) Embodiment 2

In Embodiment 1, it was proposed that, in transmitting two differentmodulated signals using two antennas, the same data be transmitted aplurality of times for only one of the modulated signals. In contrast,in this embodiment it is proposed that, in transmitting three differentmodulated signals using three antennas, the same data be transmitted aplurality of times for one or two of the three modulated signals, andassociated actual frame configurations and apparatus configurations aredescribed.

FIG. 15, in which parts corresponding to those in FIG. 2A are assignedthe same codes as in FIG. 2A, shows sample frame configurations ofmodulated signals according to this embodiment. In this embodiment, amodulated signal C is transmitted at the same time as modulated signal Aand modulated signal B. Modulated signal C contains a radio wavepropagation environment estimation symbol 1401. Reference codes 1402 and1403 denote data symbols. Modulated signal C time i data symbol 1402(S3(i)) and time i+1 data symbol 1403 (S3(i+1)) have mutually differentdata that has undergone signal point arrangement in accordance with thesame mapping rule, as in the case of modulated signal B. That is to say,modulated signal A is a special signal in which the same data istransmitted a plurality of times, changing the signal point arrangementmode, while modulated signals B and C are typical modulated signals.

FIG. 17 shows the relationship between transmitting antennas 1601, 1602,and 1603 and receiving antennas 1604, 1605, and 1606 according to thisembodiment, and the propagation paths between these transmitting andreceiving antennas.

FIG. 18, in which parts corresponding to those in FIG. 4 are assignedthe same codes as in FIG. 4, shows a sample configuration of atransmitting apparatus according to this embodiment. In transmittingapparatus 1700, a modulation section 1702 has transmit digital signal1701 and frame configuration signal 324 as input, and outputs a transmitquadrature baseband signal 1703. Spreading section 1704 spreads transmitquadrature baseband signal 1703 and outputs a post-spreading transmitquadrature baseband signal 1705.

A radio section 1706 converts post-spreading transmit quadraturebaseband signal 1705 from baseband frequency to radio frequency, andoutputs a post-conversion modulated signal 1707. A power amplifier 1708amplifies the power of modulated signal 1707, and outputs apost-amplification modulated signal 1709. Modulated signal 1709 isoutput from antenna 1603 as a radio wave.

FIG. 19, in which parts corresponding to those in FIG. 6 are assignedthe same codes as in FIG. 6, shows a sample configuration of a receivingapparatus according to this embodiment. In receiving apparatus 1800, aradio section 1803 has a received signal 1802 received by an antenna1606 as input, and outputs a received quadrature baseband signal 1804. Adespreading section 1805 has received quadrature baseband signal 1804 asinput, and outputs a post-despreading received quadrature basebandsignal 1806.

A modulated signal A transmission path estimation section 1807 haspost-despreading received quadrature baseband signal 1806 as input, andoutputs a modulated signal A transmission path estimation signal 1808. Amodulated signal B transmission path estimation section 1809 haspost-despreading received quadrature baseband signal 1806 as input, andoutputs a modulated signal B transmission path estimation signal 1810.

A modulated signal C transmission path estimation section 1811 haspost-despreading received quadrature baseband signal 1806 as input, andoutputs a modulated signal C transmission path estimation signal 1812. Amodulated signal C transmission path estimation section 1813 haspost-despreading received quadrature baseband signal 506 as input, andoutputs a modulated signal C transmission path estimation signal 1814. Amodulated signal C transmission path estimation section 1815 haspost-despreading received quadrature baseband signal 516 as input, andoutputs a modulated signal C transmission path estimation signal 1816.

Frame synchronization section 521 has post-despreading receivedquadrature baseband signals 506, 516, and 1806 as input, and outputsframe synchronization signal 522.

A demodulation section 1820 has post-despreading received quadraturebaseband signals 506, 516, and 1806, modulated signal A transmissionpath estimation signals 508, 518, and 1808, modulated signal Btransmission path estimation signals 510, 520, and 1810, modulatedsignal C transmission path estimation signals 1812, 1814, and 1816, andframe synchronization signal 522 as input, and by performingdemodulation of modulated signal A, modulated signal B, and modulatedsignal C, obtains modulated signal A received digital signal 524,modulated signal B received digital signal 525, and a modulated signal Creceived digital signal 1817, and outputs these signals.

FIG. 20 shows the detailed configuration of demodulation section 1820. Amodulated signal A, B, C demodulation section 1913 has modulated signalA transmission path estimation signals 508, 518, and 1808, modulatedsignal B transmission path estimation signals 510, 520, and 1810,modulated signal C transmission path estimation signals 1814, 1816, and1812, post-despreading received quadrature baseband signals 506, 516,and 1806, and frame synchronization signal 522 as input, and outputsmodulated signal A received digital signal 524, modulated signal Breceived digital signal 525-1, a modulated signal C received digitalsignal 1817-1, a first soft decision value signal 1917, and a secondsoft decision value signal 1918.

A modulated signal B and C demodulation section 1919 has first softdecision value signal 1917, second soft decision value signal 1918, andframe synchronization signal 522 as input, and outputs modulated signalB received digital signal 525-2 and a modulated signal C receiveddigital signal 1817-2.

Next, the operation of this embodiment will be explained.

As described above, when transmitting apparatus 1700 of this embodimenttransmits three modulated signals A, B, and C from separate antennas,the same data is transmitted a plurality of times, changing the mappingpattern (changing the signal point arrangement mode), for modulatedsignal A only. Thus, to consider a comparison with use of space-timeblock coding, whereas the same information is transmitted repeatedly bya plurality of antennas in space-time block coding, transmittingapparatus 1700 transmits data repeatedly from only one of threeantennas, thereby enabling a higher data transmission speed to bemaintained than when space-time block coding is used.

Also, by receiving such signals, receiving apparatus 1800 can demodulatemodulated signals A, B, and C with good error rate performances. That isto say, when such signals are received, the signal point arrangements ofthe received modulated signals vary between time i and time i+1, andtherefore the precision of demodulation of modulated signal A, modulatedsignal B, and modulated signal C at time i and the precision ofdemodulation of modulated signal A, modulated signal B, and modulatedsignal C at time i+1 are different. Then by demodulating modulatedsignal A at a time when demodulation precision is good, and demodulatingmodulated signal B and modulated signal C using that result, thedemodulation precision of modulated signal B and modulated signal C canbe improved.

The operation of receiving apparatus 1800 will now be explained indetail.

First, using radio wave propagation environment estimation symbols,receiving apparatus 1800 estimates channel fluctuations between thetransmitting and receiving antennas. In the case of thetransmitting/receiving antenna relationship in FIG. 7, if the channelfluctuation from transmitting antenna i to receiving antenna j isdesignated hji, and a transmit signal of receiving antenna j isdesignated Rj, the transmit/received signal relationship at time i canbe expressed by the following equation.

$\begin{matrix}{\begin{pmatrix}{R\; 1(i)} \\{R\; 2(i)} \\{R\; 3(i)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(i)} & {h\; 12(i)} & {h\; 13(i)} \\{h\; 21(i)} & {h\; 22(i)} & {h\; 23(i)} \\{h\; 31(i)} & {h\; 32(i)} & {h\; 33(i)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)} \\{S\; 2(i)} \\{S\; 3(i)}\end{pmatrix}}} & (8)\end{matrix}$

Similarly, the relationship in the following equation holds true at timei+1.

$\begin{matrix}{\begin{pmatrix}{R\; 1\left( {i + 1} \right)} \\{R\; 2\left( {i + 1} \right)} \\{R\; 3\left( {i + 1} \right)}\end{pmatrix} = {\begin{pmatrix}{h\; 11\left( {i + 1} \right)} & {h\; 12\left( {i + 1} \right)} & {h\; 13\left( {i + 1} \right)} \\{h\; 21\left( {i + 1} \right)} & {h\; 22\left( {i + 1} \right)} & {h\; 23\left( {i + 1} \right)} \\{h\; 31\left( {i + 1} \right)} & {h\; 32\left( {i + 1} \right)} & {h\; 33\left( {i + 1} \right)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)^{\prime}} \\{S\; 2\left( {i + 1} \right)} \\{S\; 3\left( {i + 1} \right)}\end{pmatrix}}} & (9)\end{matrix}$

S1(i), S2(i), and S3(i) can be obtained from the relationship inequation (8), and S1(i)′, S2(i+1), and S3(i+1) can be obtained from therelationship in equation (9).

In the same way as in Embodiment 1, h11(i)≈h11(i+1), h12(i)≈h12(i+1),h13(i)≈h13(i+1), h21(i)≈h21(i+1), h22(i)≈h22(i+1), h23(i)≈h23(i+1),h31(i)≈h31(i+1), h32(i)≈h32(i+1), and h33(i)≈h33(i+1).

At this time, the matrices of equation (8) and equation (9) are almostequal matrices, but the (S1(i), S2(i), S3(i)) and (S1(i)′, S2(i+1),S3(i+1)) vectors are different, and therefore the likelihoods of theobtained data are different.

Transmitting apparatus 1700 and receiving apparatus 1800 of thisembodiment make use of this characteristic to improve receive dataquality.

The actual demodulation (decoding) procedure of receiving apparatus 1800is as follows.

<1> Time i detection is performed, and (S1(i), S2(i), S3(i)) isobtained.<2> Time i+1 detection is performed, and (S1(i)′, S2(i+1), S3(i+1)) isobtained.<3> The time i and time i+1 reception qualities are compared.

If the time i reception quality is better, (S1(i), S2(i), S3(i)) dataobtained in time i detection is used directly. Then S1(i)′ of time i+1is estimated from S1(i) obtained in time i detection, and S2(i+1) andS3(i+1) are obtained using that result.

If the time i+1 reception quality is better, (S1(i)′, S2(i+1), S3(i+1))data obtained in time i+1 detection is used directly. Then S1(i) of timei is estimated from S1(i)′ obtained in time i+1 detection, and S2(i) andS3(i) are obtained using that result.

In receiving apparatus 1800, modulated signal A received digital signal524, modulated signal B received digital signal 525, and modulatedsignal C received digital signal 1817 are obtained by performing thiskind of demodulation processing in demodulation section 1820.

In the example in this embodiment, modulated signal A, modulated signalB, and modulated signal C are all QPSK modulated signals, and it istherefore possible to transmit a total of 6 bits—2 bits in modulatedsignal A, 2 bits in modulated signal B, and 2 bits in modulated signalC—at the same time. That is to say, it is possible to transmit 000000,000001, . . . , 111111. It is assumed that the upper 2 bits are the 2bits transmitted in modulated signal A, the middle 2 bits are the 2 bitstransmitted in modulated signal B, and the lower 2 bits are the 2 bitstransmitted in modulated signal C.

The overall operation of demodulation section 1820 will first beexplained.

First, at time i in FIG. 15, demodulation section 1820 finds signalpoints (candidate signal points) in the 64 signal point (000000, 000001,. . . , 111111) I-Q plane using modulated signal A transmission pathestimation signal 508, modulated signal B transmission path estimationsignal 510, and modulated signal C transmission path estimation signal1814. Demodulation section 1820 also has received quadrature basebandsignal 506 from despreading section 505 as input, and finds thereception state (received signal point) in the I-Q plane from thispost-despreading received quadrature baseband signal 506.

Next, demodulation section 1820 calculates, for example, the square ofthe distance from the received signal point in the I-Q plane for all 64signal points. That is to say, the square of the distance between thesignal point of transmit bits 000000 and the received signal point(X000000(i)) is found, and in the same way the squares of the distancesbetween the signal points of transmit bits 000001, . . . , 111111 andthe received signal point (X000001(i), . . . , X111111(i)) are found.

Similarly, at time i in FIG. 15, demodulation section 1820 finds signalpoints (candidate signal points) in the 64 signal point (000000, 000001,. . . , 111111) I-Q plane using modulated signal A transmission pathestimation signal 518, modulated signal B transmission path estimationsignal 520, and modulated signal C transmission path estimation signal1816. Demodulation section 1820 also has received quadrature basebandsignal 516 from despreading section 515 as input, and finds thereception state (received signal point) in the I-Q plane from thispost-despreading received quadrature baseband signal 516.

Next, demodulation section 1820 calculates, for example, the square ofthe distance from the received signal point in the I-Q plane for all 64signal points. That is to say, the square of the distance between thesignal point of transmit bits 000000 and the received signal point(Y000000(i)) is found, and in the same way the squares of the distancesbetween the signal points of transmit bits 000001, . . . , 111111 andthe received signal point (Y000001(i), . . . , Y111111(i)) are found.

Similarly, at time i in FIG. 15, demodulation section 1820 finds signalpoints (candidate signal points) in the 64 signal point (000000, 000001,. . . , 111111) I-Q plane using modulated signal A transmission pathestimation signal 1808, modulated signal B transmission path estimationsignal 1810, and modulated signal C transmission path estimation signal1812. Demodulation section 1820 also has received quadrature basebandsignal 1806 from despreading section 1805 as input, and finds thereception state (received signal point) in the I-Q plane from thispost-despreading received quadrature baseband signal 1806.

Next, demodulation section 1820 calculates, for example, the square ofthe distance from the received signal point in the I-Q plane for all 64signal points. That is to say, the square of the distance between thesignal point of transmit bits 000000 and the received signal point(Z000000(i)) is found, and in the same way the squares of the distancesbetween the signal points of transmit bits 000001, . . . , 111111 andthe received signal point (Z000001(i), . . . , Z111111(i)) are found.

Demodulation section 1820 then finds the sum of X000000(i) andY000000(i) and Z000000(i), K000000(i)=X000000(i)+Y000000(i)+Z000000(i),and similarly finds K000001(i), . . . , K111111(i). In the same way,demodulation section 1820 finds K000000(i+1), K000001(i+1), . . . ,K111111(i+1) for time i+1.

Next, demodulation section 1820 compares the likelihoods of time i andtime i+1 receive data.

For example, demodulation section 1820 searches for the smallest valueamong K000000(i), K000001(i), . . . , K111111(i). Let that value bedesignated F(i). Then demodulation section 1820 searches for thesecond-smallest value. Let that value be designated S(i).

Similarly, demodulation section 1820 searches for the smallest valueamong K000000(i+1), K000001(i+1), . . . , K111111(i+1). Let that valuebe designated F(i+1). Then demodulation section 1820 searches for thesecond-smallest value. Let that value be designated S(i+1).

Then, for example, demodulation section 1820 finds R(i)=F(i)/S(i), andR(i+1)=F(i+1)/S(i+1).

When R(i+1)>R(i), demodulation section 1820 determines that the time ireception quality is better, and determines that the 6 bits providingF(i) are correct data. Then, as the 2 bits transmitted in modulatedsignal A, the 2 bits obtained at time i are taken as time i and time i+1receive data. For modulated signals B and C, as the 2 bits transmittedrespectively at time i, the 2 bits obtained at time i are taken directlyas receive data, while the 2 bits transmitted at time i+1 are determinedmaking use of the fact that the 2 bits transmitted at time i+1 modulatedsignal A have already been determined.

For example, if the 2 bits transmitted in modulated signal A are 00, the2 bits transmitted in modulated signal B and the 2 bits transmitted inmodulated signal C at time i+1 are determined by searching for the itemwith the smallest value among the 16 points K000000(i+1), K000001(i+1),K000010(i+1), K000011(i+1), K000100(i+1), K000101(i+1), K000110(i+1),K000111(i+1), K001000(i+1), K001001(i+1), K001010(i+1), K001011(i+1),K01100(i+1), K001101(i+1), K001110(i+1), and K001111(i+1).

The 2 bits transmitted in modulated signal B and the 2 bits transmittedin modulated signal C at time i+1 are also determined in the same waywhen the 2 bits transmitted in modulated signal A are 01, 10, or 11.

When R(i)>R(i+1), demodulation section 1820 determines that the time i+1reception quality is better, and determines that the 6 bits providingF(i+1) are correct data. Then, as the 2 bits transmitted in modulatedsignal A, the 2 bits obtained at time i+1 are taken as time i and timei+1 receive data. For modulated signals B and C, as the 2 bitstransmitted respectively at time i+1, the 2 bits obtained at time i+1are taken directly as receive data, while the 2 bits transmitted at timei are determined making use of the fact that the 2 bits transmitted attime i modulated signal A have already been determined.

For example, if the 2 bits transmitted in modulated signal A are 00, the2 bits transmitted in modulated signal B and the 2 bits transmitted inmodulated signal C at time i are determined by searching for the itemwith the smallest value among the 16 points K000000(i), K000001(i),K000010(i), K000011(i), K000100(i), K000101(i), K000110(i), K000111(i),K001000(i), K001001(i), K001010(i), K001011(i), K01100(i), K001101(i),K001110(i), and K001111(i).

The 2 bits transmitted in modulated signal B and the 2 bits transmittedin modulated signal C at time i are also determined in the same way whenthe 2 bits transmitted in modulated signal A are 01, 10, or 11. Theoperation when demodulation section 1820 is configured as shown in FIG.20 will now be explained.

As described above, of the data transmitted in modulated signal A attime i and time i+1, modulated signal A, B, C demodulation section 1913outputs data demodulated from the signal of a time of good receptionquality as modulated signal A received digital signal 524.

Also, modulated signal A, B, C demodulation section 1913 outputsreceived digital signal 525-1 of modulated signal B and received digitalsignal 1817-1 of modulated signal C of either time i or time i+1.Furthermore, modulated signal A, B, C demodulation section 1913 outputsK000000(i), . . . , K111111(i) as first soft decision value signal 1917,and outputs K000000(i+1), . . . , K111111(i+1) as second soft decisionvalue signal 1918.

Modulated signal B and C demodulation section 1919 has K000000(i), . . ., K111111(i) comprising first soft decision value signal 1917 andK000000(i+1), . . . , K111111(i+1) comprising second soft decision valuesignal 1918 as input, and, as described above, by performing modulatedsignal B and modulated signal C demodulation based on the time i andtime i+1 reception qualities, obtains modulated signal B receiveddigital signal 525-2 of a different time from modulated signal B fromwhich received digital signal 525-1 was obtained, and also obtainsmodulated signal C received digital signal 1817-2 of a different timefrom modulated signal B from which received digital signal 1817-1 wasobtained.

Thus, according to this embodiment, of modulated signals A, B, and Ctransmitted from different antennas, modulated signal A is formed bymodulating the same data a plurality of times while changing the signalpoint arrangement mode, and modulated signals B and C are formed not bymodulating the same data a plurality of times while changing the signalpoint arrangement mode but by performing sequential modulation of timeseries data (that is, by executing normal modulation), thereby enablingthe error rate performances of the data stream transmitted a pluralityof times to be improved, and as a result, the error rate performances ofall three streams to be improved, while maintaining a higher datatransmission speed than when space-time block coding is used.

Actually, on the receiving side, by taking the demodulation result ofmodulated signal A obtained based on a received signal of a time of goodreception quality as the modulated signal A received digital signal, andobtaining the received digital signals of modulated signals B and Creceived at a time of poor reception quality from a received signal ofthat time of poor reception quality using the already determinedmodulated signal A received digital signal of a time of good receptionquality, the error rate performances of modulated signals B and Creceived at a time of poor reception quality can also be improved.

(2-1) Variant Example 1

In this embodiment a case has been described in which the frameconfigurations transmitted by transmitting apparatus 1700 are as shownin FIG. 15, but the transmitted frame configurations may also be asshown in FIG. 16. The difference between the frame configurations inFIG. 16 and the frame configurations in FIG. 15 is that the timedifference in transmitting signal S1(i) in which the same data ismodulated in modulated signal A is made small in the case of FIG. 15,but is made very large in FIG. 16.

Consequently, the radio wave propagation environment is totallydifferent at time i and time j. Considering this, in the case of FIG.16, the signal point arrangement of modulated signal A transmitted attime j is made the same as the signal point arrangement of modulatedsignal A transmitted at time i. This is because it was considered that,even if the signal point arrangement of modulated signal A is notintentionally varied, the time i and time j reception qualities willdiffer to some extent due to differences in the radio wave propagationenvironment.

As a result, if the demodulation result of modulated signal A obtainedbased on a received signal of a time of good reception quality is takenas the modulated signal A received digital signal, and the receiveddigital signals of modulated signals B and C received at a time of poorreception quality from a received signal of that time of poor receptionquality are obtained using the already determined modulated signal Areceived digital signal of a time of good reception quality, the errorrate performances of modulated signals B and C received at a time ofpoor reception quality can also be improved in the same way as whensignals with the frame configurations shown in FIG. 15 are transmitted.

This will now be explained in specific terms. Equation (8) given aboveholds true at time i. Similarly, the relationship in the followingequation holds true at time j.

$\begin{matrix}{\begin{pmatrix}{R\; 1(j)} \\{R\; 2(j)} \\{R\; 3(j)}\end{pmatrix} = {\begin{pmatrix}{h\; 11(j)} & {h\; 12(j)} & {h\; 13(j)} \\{h\; 21(j)} & {h\; 22(j)} & {h\; 23(j)} \\{h\; 31(j)} & {h\; 32(j)} & {h\; 33(j)}\end{pmatrix}\begin{pmatrix}{S\; 1(i)} \\{S\; 2(j)} \\{S\; 3(j)}\end{pmatrix}}} & (10)\end{matrix}$

In receiving apparatus 1800, h11(j), h12(j), h13(j), h21(j), h22(j),h23(j), h31(j), h32(j), and h33(j) in equation (10) are estimated using,for example, radio wave propagation environment estimation symbols 801,803, and 1503 in FIG. 16. Here, since the radio wave propagationenvironment differs for time i and time j, h11(i)≠h11(j), h12(i)≠h12(j),h13(i)≠h13(j), h21(i)≠h21(j), h22(i)≠h22(j), h23(i)≠h23(j),h31(i)≠h31(j), h32(i)≠h32(j), and h33(i)≠h33(j). Therefore, time i andtime j reception qualities are totally different. A description will nowbe given of signal point arrangements in the I-Q plane for time i andtime j taking the above into consideration.

Examples of modulated signal A signal point arrangements in the I-Qplane are shown in FIG. 3A through FIG. 3C. When the frameconfigurations shown in FIG. 16 are used, the time i and j signal pointarrangements may both be as shown in FIG. 3A, or may differ, with thetime i signal point arrangement as shown in FIG. 3A and the time jsignal point arrangement as shown in FIG. 3B. This is because, unlike inthe case of the frame configurations in FIG. 15, the radio wavepropagation environment differs for times i and j, and therefore even ifthe signal point arrangement is not intentionally varied at times i andj, the reception quality is different for time i and time j.

The decoding procedure is described in detail below. This can beconsidered as similar to the operation in the case of the frameconfigurations in FIG. 15. That is to say, time i+1 operations can bethought of as being replaced by time j operations.

<1> Time i detection is performed, and (S1(i), S2(i), S3(i)) isobtained.<2> Time j detection is performed, and (S1(i) S2(j), S3(j)) is obtained.<3> The time i and time j reception qualities are compared.

If the time i reception quality is better, (S1(i), S2(i), S3(i)) dataobtained in time i detection is used directly. Then S1(i) of time j isestimated from S1(i) obtained in time i detection, and S2(j) and S3(j)are obtained using that result.

If the time j reception quality is better, (S1(i) S2(j), S3(j)) dataobtained in time j detection is used directly. Then S1(i) of time i isestimated from S1(i) obtained in time j detection, and S2(i) and S3(i)are obtained using that result.

In receiving apparatus 1800, modulated signal A received digital signal524, modulated signal B received digital signal 525, and modulatedsignal C received digital signal 1817 are obtained by performing thiskind of demodulation processing in demodulation section 1820.

A description of the detailed operation of demodulation section 1820when transmit signals with the frame configurations in FIG. 16 arereceived will be omitted, as it is the same as described above with“time j” substituted for “time i+1” operations. However, a difference inabove time i+1 and time j processing is that, whereas for time i+1, timei+1 data likelihood is determined based on signal points (candidatesignal points) obtained using radio wave propagation environmentestimation symbols 101, 104, and 1401 in FIG. 15, for time j, time jdata likelihood is determined based on signal points (candidate signalpoints) obtained using radio wave propagation environment estimationsymbols 801, 803, and 1503 in FIG. 16.

(2-2) Variant Example 2

Here, an example will be described in which the frame configurationstransmitted by transmitting apparatus 1700 are as shown in FIG. 21instead of FIG. 15. The difference between the frame configurations inFIG. 21 and the frame configurations in FIG. 15 is that the timedifference in transmitting signal S1(i) and S1(i)′ in which the samedata is modulated in modulated signal A is “1” in the case of FIG. 15,but is n in FIG. 21.

Here, if n is such that the relationships h11(i)≈h11(i+n),h12(i)≈h12(i+n), h21(i)≈h21(i+n), and h22(i)≈h22(i+n) hold true, thesame kind of result can be obtained as when signals with the frameconfigurations in FIG. 15 are transmitted. That is to say, operationscan be executed in the same way, considering a time i+1 operation as atime i+n operation.

(2-3) Variant Example 3

Here, it is proposed that the frame configurations transmitted bytransmitting apparatus 1700 be as shown in FIG. 22 instead of as shownin FIG. 15. The frame configurations in FIG. 22 will first be explained.In modulated signal A, the same information is transmitted at time i,time i+1, time i+2, and time i+3. Then, for example, the S1(i) signalpoint arrangement is made as shown in FIG. 3A, the S1(i)′ signal pointarrangement as shown in FIG. 3B, the S1(i)″ signal point arrangement asshown in FIG. 3C, and the S1(i)″′ signal point arrangement is made adifferent arrangement from those shown in FIG. 3A, FIG. 3B, and FIG. 3C.Thus, in modulated signal A, the same information is transmitted withdifferent signal point arrangements at times i, i+1, i+2, and i+3.Although different signal point arrangements need not necessarily beused, transmitting with different signal point arrangements has theeffect of increasing the probability of the time i, i+1, i+2, and i+3reception qualities being different.

In modulated signal B, the same information is transmitted at times iand i+1, and the same information is transmitted at times i+2 and i+3.For example, at time i, S2(i) is transmitted with the signal pointarrangement in FIG. 3A; at time i+1, S2(i)′ is transmitted with thesignal point arrangement in FIG. 3B; at time i+2, S2(i+2) is transmittedwith the signal point arrangement in FIG. 3A; and at time i+3, S2(i+2)′is transmitted with the signal point arrangement in FIG. 3B.

In modulated signal C, different information is transmitted at times i,i+1, i+2, and i+3. The modulated signal C signal point arrangement maybe as shown in FIG. 3A, for example.

As described above, the same information is transmitted four times inmodulated signal A, and the same information is transmitted twice inmodulated signal B. By changing the number of times the same informationis transmitted in modulated signal A and modulated signal B in this way,demodulation operation is made possible whereby modulated signal A isdemodulated, then modulated signal B is demodulated, and then modulatedsignal C is demodulated. By this means, reception quality can beimproved further than in the case of the embodiment, and the datatransmission speed can be improved.

Signals with the frame configurations shown in FIG. 22 can be formed,for example, by a transmitting apparatus 2200 with the configurationshown in FIG. 23. In FIG. 23, in which parts corresponding to those inFIG. 18 are assigned the same codes as in FIG. 18, transmittingapparatus 2200 differs from transmitting apparatus 1700 in FIG. 18 inhaving a coding section 2201.

Coding section 2201 has modulated signal B transmit digital signal 313and frame configuration signal 324 as input, and obtains a modulatedsignal B transmit digital signal 2202 by coding transmit digital signal313 in accordance with the frame configuration in FIG. 22, and outputsthis transmit digital signal 2202.

Transmit signals with the frame configurations in FIG. 22 transmittedfrom transmitting apparatus 2200 are received by receiving apparatus1800 shown in FIG. 19. When demodulating transmit signals with the frameconfigurations in FIG. 22, demodulation section 1820 may have theconfiguration shown in FIG. 24, for example.

Demodulation section 1820 in FIG. 24 will now be described.

A modulated signal A demodulation section 2301 has modulated signal Atransmission path estimation signals 508, 518, and 1808, modulatedsignal B transmission path estimation signals 510, 520, and 1810,modulated signal C transmission path estimation signals 1814, 1816, and1812, post-despreading received quadrature baseband signals 506, 516,and 1806, and frame synchronization signal 522 as input, and outputsmodulated signal A received digital signal 524, a first soft decisionvalue signal 2303, a second soft decision value signal 2304, a thirdsoft decision value signal 2305, and a fourth soft decision value signal2306.

A modulated signal B demodulation section 2307 has first soft decisionvalue signal 2303, second soft decision value signal 2304, third softdecision value signal 2305, fourth soft decision value signal 2306,modulated signal A received digital signal 524, and framesynchronization signal 522 as input, and outputs modulated signal Breceived digital signal 525, a first soft decision value signal 2309, asecond soft decision value signal 2310, a third soft decision valuesignal 2311, and a fourth soft decision value signal 2312.

A modulated signal C demodulation section 2313 has first soft decisionvalue signal 2309, second soft decision value signal 2310, third softdecision value signal 2311, fourth soft decision value signal 2312,modulated signal A received digital signal 524, modulated signal Breceived digital signal 525, and frame synchronization signal 522 asinput, and outputs modulated signal C received digital signal 1817.

Next, the operation of demodulation section 1820 when transmit signalswith the frame configurations in FIG. 22 are received will be described.Using modulated signals at times i, i+1, i+2, and i+3 in the frameconfigurations in FIG. 22, modulated signal A demodulation section 2301outputs modulated signal A received digital signal 524 by demodulatingmodulated signal A, and outputs the time i soft decision value signal asfirst soft decision value signal 2303, the time i+1 soft decision valuesignal as second soft decision value signal 2304, the time i+2 softdecision value signal as third soft decision value signal 2305, and thetime i+3 soft decision value signal as fourth soft decision value signal2306.

Then modulated signal B demodulation section 2307 has first softdecision value signal 2303, second soft decision value signal 2304,third soft decision value signal 2305, fourth soft decision value signal2306, and modulated signal A received digital signal 524 as input, andemploying the modulated signal A received digital signal 524 result andusing first soft decision value signal 2303 and second soft decisionvalue signal 2304, demodulates information S2(i) and S2(i)′ transmittedat times i and i+1 of modulated signal B in FIG. 22. Also, employing themodulated signal A received digital signal 524 result and using thirdsoft decision value signal 2305 and fourth soft decision value signal2306, modulated signal B demodulation section 2307 demodulatesinformation S2(i+2) and S2(i+2)′ transmitted at times i+2 and i+3 ofmodulated signal B in FIG. 22. Then modulated signal B demodulationsection 2307 outputs these demodulation results as modulated signal Breceived digital signal 525.

Modulated signal C demodulation section 2313 has first soft decisionvalue signal 2309, second soft decision value signal 2310, third softdecision value signal 2311, fourth soft decision value signal 2312,modulated signal A received digital signal 524, and modulated signal Breceived digital signal 525 as input, and employing modulated signal Areceived digital signal 524 and modulated signal B received digitalsignal 525, and using first soft decision value signal 2309, demodulatesinformation S3(i) of modulated signal C transmitted at time i.Similarly, employing modulated signal A received digital signal 524 andmodulated signal B received digital signal 525, and using second softdecision value signal 2310, modulated signal C demodulation section 2313demodulates information S3(i+1) transmitted in modulated signal C oftime i+1, Similarly, employing modulated signal A received digitalsignal 524 and modulated signal B received digital signal 525, and usingthird soft decision value signal 2311, modulated signal C demodulationsection 2313 demodulates information S3(i+2) transmitted in modulatedsignal C of time i+2. Similarly, employing modulated signal A receiveddigital signal 524 and modulated signal B received digital signal 525,and using fourth soft decision value signal 2312, modulated signal Cdemodulation section 2313 demodulates information S3(i+3) transmitted inmodulated signal C of time i+3.

Thus, by transmitting modulated signals with the same data a pluralityof times in modulated signal A and modulated signal B, and making thenumber of times the same data is transmitted in modulated signal Agreater than the number of times the same data is transmitted inmodulated signal B, demodulated data with good error rate performancescan be obtained for all of modulated signals A, B, and C on thereceiving side by first performing demodulation of modulated signal A,then performing demodulation of modulated signal B based on themodulated signal A demodulation result, and then performing modulatedsignal C demodulation based on the modulated signal A and modulatedsignal B demodulation results. Also, error rate performances can beimproved while maintaining a higher data transmission speed than whenspace-time block coding is used.

(2-4) Variant Example 4

Here, it is proposed that the frame configurations transmitted bytransmitting apparatus 1700 be as shown in FIG. 25. In FIG. 25, partscorresponding to those in FIG. 22 are assigned the same codes as in FIG.22. The difference between the frame configurations in FIG. 25 and theframe configurations in FIG. 22 is that, in the frame configurations inFIG. 22 modulated symbols of the same data are transmitted at time 1intervals, whereas in the frame configurations in FIG. 25 modulatedsymbols of the same data are transmitted at time n intervals.

Here, if n is such that the relationshipsh11(i)≈h11(i+n)≈h11(i+2n)≈h11(i+3n),h12(i)≈h12(i+n)≈h12(i+2n)≈h12(i+3n),h13(i)≈h13(i+n)≈h13(i+2n)≈h13(i+3n),h21(i)≈h21(i+n)≈h21(i+2n)≈h21(i+3n),h22(i)≈h22(i+n)≈h22(i+2n)≈h22(i+3n),h23(i)≈h23(i+n)≈h23(i+2n)≈h23(i+3n),h31(i)≈h31(i+n)≈h31(i+2n)≈h31(i+3n),h32(i)≈h32(i+n)≈h32(i+2n)≈h32(i+3n), andh33(i)≈h33(i+n)≈h33(i+2n)≈h33(i+3n) hold true, operations can beexecuted in the same way as when signals with the frame configurationsin FIG. 22 are transmitted. That is to say, operations can be executedin the same way as in the description of frame configurations in FIG.22, considering a FIG. 22 time i+1 operation as a FIG. 25 time i+noperation, a FIG. 22 time i+2 operation as a FIG. 25 time i+2noperation, and a FIG. 22 time i+3 operation as a FIG. 25 time i+3noperation.

(2-5) Variant Example 5

Here, it is proposed that the frame configurations transmitted bytransmitting apparatus 1700 be as shown in FIG. 26. In FIG. 26, partscorresponding to those in FIG. 22 are assigned the same codes as in FIG.22. The difference between the frame configurations in FIG. 26 and theframe configurations in FIG. 22 is that, in the frame configurations inFIG. 22 modulated symbols of the same data are transmitted at time 1intervals, whereas in the frame configurations in FIG. 26 modulatedsymbols of the same data are transmitted at times i, j, k, and m.

Here, the following relationships hold true;h11(i)≠h11(j)≠h11(k)≠h11(m), h12(i)≠h12(j)≠h12(k)≠h12(m),h13(i)≠h13(j)≠h13(k)≠h13(m), h21(i)≠h21(j)≠h21(k)≠h21(m),h22(i)≠h22(j)≠h22(k)≠h22(m), h23(i)≠h23(j)≠h23 (k)≠h23(m),h31(i)≠h31(j)≠h31(k)≠h31(m), h32(i)≠h32(j)≠h32(k)≠h32(m),h33(i)≠h33(j)≠h33(k)≠h33(m).

Operations can be executed in the same way as in the description offrame configurations in FIG. 22, considering a FIG. 22 time i+1operation as a FIG. 26 time j operation, a FIG. 22 lime i+2 operation asa FIG. 26 time k operation, and a FIG. 22 time i+3 operation as a FIG.26 time m operation. However, in the frame configurations in FIG. 26,symbols for estimating the time j radio wave propagation environment arenecessary separately from radio wave propagation environment estimationsymbols 2101, 2106, and 2111. Similarly, symbols for estimating the timek radio wave propagation environment are necessary separately from radiowave propagation environment estimation symbols 2101, 2106, and 2111,and symbols for estimating the time m radio wave propagation environmentare necessary separately from radio wave propagation environmentestimation symbols 2101, 2106, and 2111.

(2-6) Variant Example 6

In this embodiment, the modulated signal A and B modulation method hasbeen described as QPSK. Below, setting methods of modulation methodssuitable for forming modulated signals A and B are considered.

For example, if 16QAM is used as the modulation method for modulatedsignals A and B, the density of signal points in the I-Q planeincreases, making it difficult to produce great changes in Euclidiandistances even if phase rotation is effected, with the result thatsignificant improvements in reception quality cannot be expected.

A possible means of solving this problem—that is, effecting phaserotation and producing changes in Euclidian distances—is to use BPSK asthe modulated signal A modulation method, and 8PSK, 16QAM, 64QAM,128QAM, or 256QAM as the modulated signal B modulation method. Anadvantage of doing this is that signal points are arranged regularly inreception. It is all the more desirable if the modulated signal Atransmission power and modulated signal B transmission power are set tosuitable values.

Some examples are given below. When modulated signal A is a QPSK signaland modulated signal B is a 16QAM signal, a suitable setting would bemodulated signal A transmission power:modulated signal B transmissionpower=2:10.

When modulated signal A is a QPSK signal and modulated signal B is a64QAM signal, a suitable setting would be modulated signal Atransmission power:modulated signal B transmission power=2:42.

When modulated signal A is a BPSK signal and modulated signal B is a16QAM signal, a suitable setting would be modulated signal Atransmission power:modulated signal B transmission power=b 2:42.

When modulated signal A is a BPSK signal and modulated signal B is a64QAM signal, a suitable setting would be modulated signal Atransmission power:modulated signal B transmission power=1:42.

(2-7) Variant Example 7

Transmitting apparatus configurations are not limited to theconfigurations in FIG. 18 and FIG. 23. Also, the receiving apparatusconfiguration is not limited to the configuration in FIG. 19, anddemodulation section configurations are not limited to theconfigurations in FIG. 20 and FIG. 24.

In this embodiment, frame configurations for transmitting three kinds ofmodulated signals, A, B, and C, have been described, but the presentinvention can be similarly implemented if n (n≧4) different modulatedsignals are transmitted Essentially, the same kind of effect as in thisembodiment can be obtained as long as there is a modulated signal thattransmits data a plurality of times among n kinds of modulated signal.

Frame configurations are not limited to those shown in FIG. 15, FIG. 16,FIG. 21, FIG. 22, FIG. 25, and FIG. 26, and the same kind of effect canbe obtained as long as the same data is transmitted a plurality oftimes, changing the signal point arrangement mode. In this embodiment,also, a frame configuration whereby the same data is transmitted twicein modulated signal A and a frame configuration whereby the same data istransmitted four times in modulated signal A have been described with aframe configuration whereby the same data is transmitted twice inmodulated signal B, but frame configurations are not limited to these,and the present invention can also be similarly implemented with frameconfigurations whereby the same data is transmitted n (n≧4) times inmodulated signals A and B. Here, as the value of n increases, theapparent data transmission speed at which transmission is possible withmodulated signals A and B declines, but error rate performances whenmodulated signals A, B, and C are demodulated improve, and thereforemaking n larger the poorer the radio wave propagation environmentenables the effective data transmission speed to be increased.

In this embodiment, coding of modulated signal A, modulated signal B,and modulated signal C is performed with respect to the time axisdirection. That is to say, in the examples in this embodiment, modulatedsignals of the same data are transmitted at different times in modulatedsignal A. However, the coding of this embodiment can be performed in thefrequency axis direction, especially when using a multicarrier system ofwhich OFDM is an example. That is to say, modulated signal A could havea plurality of identical data symbols placed on different carriers.

In this embodiment, improving the reception quality of modulated signalA also improves the reception quality of modulated signal B andmodulated signal C.

In addition, improving the reception quality of modulated signal B alsoimproves the reception quality of modulated signal C. If, in addition tothis embodiment, block coding, convolutional coding such as Viterbicoding or turbo coding, or coding such as LDPC coding, is executed onmodulated signals A and B, the reception quality of modulated signals Aand B can be further improved, enabling the reception quality ofmodulated signal C also to be further improved.

Block coding, convolutional coding such as Viterbi coding or turbocoding, and error correction coding such as LDPC coding, are not limitedto execution on modulated signals A and B only, but may be executed forall of modulated signals A, B, and C. In this case, modulated signals Band C are demodulated after demodulation of modulated signal A.

(3) Embodiment 3

In this embodiment, a case is described in which Embodiment 1,Embodiment 2, and OFDM are combined.

FIG. 27 shows a sample configuration of a transmitting apparatusaccording to this embodiment. A coding section 2602 has a modulatedsignal A transmit digital signal 2601 and frame configuration signal2624 as input, and outputs a post-coding transmit digital signal 2603. Amodulation section 2625 has post-coding transmit digital signal 2603 andframe configuration signal 2624 as input, and outputs a transmitquadrature baseband signal 2626 in accordance with frame configurationsignal 2624. A serial/parallel conversion section 2604 has transmitorthogonal baseband signal 2626 and frame configuration signal 2624 asinput, and outputs a parallel signal 2605. An inverse Fourier transformsection 2606 has parallel signal 2605 as input, and outputs apost-inverse-Fourier-transform signal 2607. A radio section 2608converts post-inverse-Fourier-transform signal 2607 from basebandfrequency to radio frequency, and outputs a post-conversion modulatedsignal 2609. A power amplifier 2610 amplifies the power of modulatedsignal 2609, and outputs a post-amplification modulated signal 2611.Modulated signal 2611 is output from an antenna 2612 as a radio wave.

A modulation section 2627 has a modulated signal B transmit digitalsignal 2613 and frame configuration signal 2624 as input, and outputs atransmit quadrature baseband signal 2628. A serial/parallel conversionsection 2614 has transmit quadrature baseband signal 2628 as input, andoutputs a parallel signal 2615. An inverse Fourier transform section2616 has parallel signal 2615 as input, and outputs apost-inverse-Fourier-transform signal 2617. A radio section 2618converts post-inverse-Fourier-transform signal 2617 from basebandfrequency to radio frequency, and outputs a post-conversion modulatedsignal 2619 amplifies the power of modulated signal 2619, and outputs apost-amplification modulated signal 2621. Modulated signal 2621 isoutput from an antenna 2622 as a radio wave.

FIG. 28 shows a sample configuration of a receiving apparatus accordingto this embodiment. A radio section 2703 has a received signal 2702received by an antenna 2701 as input, and outputs a received quadraturebaseband signal 2704. A Fourier transform section 2705 has receivedquadrature baseband signal 2704 as input, and outputs apost-Fourier-transform signal 2706.

A modulated signal A transmission path estimation section 2707 haspost-Fourier-transform signal 2706 as input, and outputs a modulatedsignal A transmission path estimation signal group 2708. A modulatedsignal B transmission path estimation section 2709 haspost-Fourier-transform signal 2706 as input, and outputs a modulatedsignal B transmission path estimation signal group 2710.

A radio section 2713 has a received signal 2712 received by an antenna2711 as input, and outputs a received quadrature baseband signal 2714. AFourier transform section 2715 has received quadrature baseband signal2714 as input, and outputs a post-Fourier-transform signal 2716.

A modulated signal A transmission path estimation section 2717 haspost-Fourier-transform signal 2716 as input, and outputs a modulatedsignal A transmission path estimation signal group 2718. A modulatedsignal B transmission path estimation section 2719 haspost-Fourier-transform signal 2716 as input, and outputs a modulatedsignal B transmission path estimation signal group 2720.

A demodulation section 2721 has modulated signal A transmission pathestimation signal groups 2708 and 2718, modulated signal B transmissionpath estimation signal groups 2710 and 2720, and post-Fourier-transformsignals 2706 and 2716 as input, and outputs a modulated signal Areceived digital signal 2722 and modulated signal B received digitalsignal 2723.

FIG. 29A and FIG. 29B show sample frame configurations according to thisembodiment, in which reference code 2801 denotes radio wave propagationenvironment estimation symbols and reference code 2802 denotes datasymbols, coded in the time axis direction. Modulated signal A is codedacross times i and i+1 in carrier 1. Modulated signal B is coded acrosstimes i and i+1 in carrier 1.

Modulated signal A transmits S1(i) at time i and S1(i)′ at time i+1 incarrier 1. Above-mentioned S1(i) and S1(i)′ are modulated symbols formedby changing the signal point arrangement of the same data.

Modulated signal B transmits S2(i) at time i and S2(i+1) at time i+1 incarrier 1. S2(i) and S2(i+1) are modulated symbols formed from differentdata.

FIG. 30A and FIG. 30B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. In the caseshown in FIG. 30A and FIG. 30B, modulated symbols are coded in thefrequency axis direction. Modulated signal A is coded across carrier 1and carrier 2 at time i. Modulated signal B is coded across carrier 1and carrier 2 at time i.

Modulated signal A transmits S1(i) in carrier 1 and S1(i)′ in carrier 2at time i.

Modulated signal B transmits S2(i−1) in carrier 1 and S2(i−2) in carrier2 at time i. Here, S2(i−1) and S2(i−2) are modulated symbols formed fromdifferent data.

FIG. 31A and FIG. 31B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. In the caseshown in FIG. 31A and FIG. 31B, modulated symbols are coded in the timeaxis direction. Modulated signal A is coded at time i and time i+n incarrier 1. Modulated signal B is coded at time i and time i+n in carrier1.

Modulated signal A transmits S1(i) at time i and S1(i)′ at time i+n incarrier 1. Modulated signal B transmits S2(i) at time i and S2(i+1) attime i+n in carrier 1.

FIG. 32A and FIG. 32B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. In the caseshown in FIG. 32A and FIG. 32B, modulated symbols are coded in thefrequency axis direction Modulated signal A is coded in carrier 1 andcarrier 1+n at time I Modulated signal B is coded in carrier 1 andcarrier 1+n at time i.

Modulated signal A transmits S1(i) in carrier 1 and S1(i)′ in carrier1+n at time i. Modulated signal B transmits S2(i−1) in carrier 1 andS2(i−2) in carrier 1+n at time i.

FIG. 33A and FIG. 33B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. In the caseshown in FIG. 33A and FIG. 33B, modulated symbols are coded in the timeaxis direction. Modulated signal A is coded at time i and time j incarrier 1. Modulated signal B is coded at time i and time j in carrier1.

Modulated signal A transmits S1(i) at time i and S1(i)′ at time j incarrier 1. Modulated signal B transmits S2(i−1) at time i and S2(i+n) attime j in carrier 1.

FIG. 34A and FIG. 34B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. In the caseshown in FIG. 34A and FIG. 34B, modulated symbols are coded in thefrequency axis direction. Modulated signal A is coded in carrier 1 andcarrier at time i. Modulated signal B is coded in carrier 1 and carrierj time i.

Modulated signal A transmits S1(i) in carrier 1 and S1(i)′ in carrier jat time i.

Modulated signal B transmits S2(i−1) in carrier 1 and S2(i−j) in carrierj at time i.

FIG. 35A and FIG. 35B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. Modulatedsignal A is coded at time i, time i+1 and time i+2 in carrier 1.Modulated signal B is coded at time i, time i+1 and time i+2 in carrier1.

Modulated signal A transmits S1(i) at time i, transmits and S1(i)′ attime i+1, and transmits S1(i)″ at time i+2, in carrier 1, Here, S1(i),S1(i)′, and S1(i)″ are modulated symbols formed by changing the signalpoint arrangement of the same data. S2(i+1) at time and transmits andS2(i+2) at time i+2, in carrier 1. Here, S2(i), S2(i+1), and S2(i+2) areobtained by demodulating different data.

FIG. 36A and FIG. 36B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. Modulatedsignal A is coded in carrier 1, carrier 2, and carrier 3 at time i.Modulated signal B is coded in carrier 1, carrier 2, and carrier 3 attime i.

Modulated signal A transmits S1(i) in carrier 1, transmits S1(i)′ incarrier 2, and transmits S1(i)″ in carrier 3, at time i. Modulatedsignal B transmits S2(i−1) in carrier 1, transmits S2(i−2) in carrier 2,and transmits S2(i−3) in carrier 3, at time i.

FIG. 37A and FIG. 37B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. Modulatedsignal A transmits the same data by means of symbols S1(i), S1(i)′, andS1(i)″ with different signal point arrangements at time i, time j, andtime k, in carrier 1 (the same signal point arrangements may also beused). Modulated signal B transmits different data by means of symbolsS1(i), S2(j), and S2(k) at time i, time j, and time k, in carrier 1.

FIG. 38A and FIG. 38B show other sample frame configurations accordingto this embodiment, with parts identical to those in FIG. 29A and FIG.29B assigned the same codes as in FIG. 29A and FIG. 29B. Modulatedsignal A transmits the same data by means of symbols S1(i), S1(i)′, andS1(i)″ with different signal point arrangements in carrier carrier j,and carrier k, at time i (the same signal point arrangements may also beused). Modulated signal B transmits different data by means of symbolsS1(i) S2(j), and S2(k) in carrier i, carrier j, and carrier k, at timei.

FIG. 39A through FIG. 39C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i) andS1(i)′ with different signal point arrangements at time i and time i+1in carrier 1. Modulated signal. B transmits different data by means ofsymbols S2(i) and S2(i+1) at time i and time i+1 in carrier 1. Modulatedsignal C transmits different data by means of symbols S3(i) and S3(i+1)at time i and time i+1 in carrier 1.

FIG. 40A through FIG. 40C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i) andS1(i)′ with different signal point arrangements in carrier 1 and carrier2 at time i. Modulated signal B transmits different data by means ofsymbols S2(1) and S2(2) in carrier 1 and carrier 2 at time i. Modulatedsignal C transmits different data by means of symbols S3(1) and S3(2) incarrier 1 and carrier 2 at time i.

FIG. 41A through FIG. 41C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i) andS1(i)′ with different signal point arrangements at time i and time j incarrier 1 (the same signal point arrangements may also be used).Modulated signal B transmits different data by means of symbols S2(i)and S2(j) at time i and time j in carrier 1. Modulated signal Ctransmits different data by means of symbols S3(i) and S3(j) at time iand time j in carrier 1.

FIG. 42A through FIG. 42C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i) andS1(i)′ with different signal point arrangements in carrier i and carrierj at time i. Modulated signal B transmits different data by means ofsymbols S2(i) and S2(j) in carrier i and carrier j at time i. Modulatedsignal C transmits different data by means of symbols S3(i) and S3(j) incarrier i and carrier j at time i.

FIG. 43A through FIG. 43C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i),S1(i)′, S1(i)″, and S1(i)″′, with different signal point arrangements attime i, time i+1, time i+2, and time i+3 in carrier 1. Modulated signalB transmits the same data by means of symbols S2(i) and S2(i)′ withdifferent signal point arrangements at time i and time i+1, andtransmits the same data by means of symbols S2(i+2) and S2(i+2)′ withdifferent signal point arrangements at time i+2 and time i+3, in carrier1. Modulated signal C transmits different data by means of symbolsS3(i), S3(i+1), S3(i+2), and S3(i+3) at time i, time i+1, time i+2, andtime i+3, in carrier 1.

FIG. 44A through FIG. 44C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i),S1(i)′, S1(i)″, and S1(i)″′, with different signal point arrangements incarrier 1, carrier 2, carrier 3, and carrier 4, at time i. Modulatedsignal B transmits the same data by means of symbols S2(1) and S2(1)′with different signal point arrangements in carrier 1 and carrier 2, andtransmits the same data by means of symbols S2(3) and S2(3)′ withdifferent signal point arrangements in carrier 3 and carrier 4, at timei. Modulated signal C transmits different data by means of symbolsS3(1), S3(2), S3(3), and S3(4) in carrier 1, carrier 2, carrier 3, andcarrier 4, at time i.

FIG. 45A through FIG. 45C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i),S1(i)′, S1(i)″, and S1(i)″′, with different signal point arrangements attime i, time j, time k, and time m in carrier 1. Modulated signal Btransmits the same data by means of symbols S2(i) and S2(i)′ withdifferent signal point arrangements at time i and time j, and transmitsthe same data by means of symbols S2(k) and S2(k)′ with different signalpoint arrangements at time k and time m, in carrier 1. Modulated signalC transmits different data by means of symbols S3(i), S3(j), S3(k), andS3(m) at time i, time j, time k, and time m in carrier 1.

FIG. 46A through FIG. 46C show other sample frame configurationsaccording to this embodiment, with parts identical to those in FIG. 29Aand FIG. 29B assigned the same codes as in FIG. 29A and FIG. 29B.Modulated signal A transmits the same data by means of symbols S1(i),S1(i)′, S1(i)″, and S1(i)″′, with different signal point arrangements incarrier i, carrier j, carrier k, and carrier m, at time i. Modulatedsignal B transmits the same data by means of symbols S2(i) and S2(i)′with different signal point arrangements in carrier i and carrier j, andtransmits the same data by means of symbols S2(k) and S2(k)′ withdifferent signal point arrangements in carrier k and carrier m, at timei. Modulated signal C transmits different data by means of symbolsS3(i), S3(j), S3(k), and S3(m) in carrier i, carrier j, carrier k, andcarrier m, at time i.

The operation of this embodiment will now be described in detail usingFIG. 2A, FIG. 2B, FIG. 3A through FIG. 3C, FIG. 5, FIG. 14, FIG. 25,FIG. 27, FIG. 28, FIG. 29A, FIG. 29B, FIG. 30A, FIG. 30B, FIG. 31A, FIG.31B, FIG. 32A, FIG. 32B, FIG. 33A, FIG. 33B, FIG. 34A, FIG. 34B, FIG.35A, FIG. 35B, FIG. 36A, FIG. 36B, FIG. 37A, FIG. 37B, FIG. 38A, FIG.38B, FIG. 39A through FIG. 39C, FIG. 40A through FIG. 40C, FIG. 41Athrough FIG. 41C, FIG. 42A through FIG. 42C, FIG. 43A through FIG. 43C,FIG. 44A through FIG. 44C, FIG. 45A through FIG. 45C, and FIG. 46Athrough FIG. 46C.

FIG. 29A and FIG. 29B show an example of the frame configurations ofmodulated signal A and modulated signal B transmitted by transmittingapparatus 2600 in FIG. 27. Modulated signal transmitted from themodulated signal A transmitting section in FIG. 27 is the modulatedsignal A frame configuration in FIG. 29A, and the frame configuration ofa modulated signal transmitted from the modulated signal B transmittingsection in FIG. 27 is the modulated signal B frame configuration in FIG.29B.

Characteristics of the frame configurations in FIG. 29A and FIG. 29B arethat modulated signal A transmits the same data by means of symbolsS1(i) and S1(i)′ with different signal point arrangements at time i andtime i+1 in carrier 1, while modulated signal B transmits different databy means of symbols S2(i) and S2(i+1) at time i and time i+1 in carrier1.

Drawings showing the S1(i) and S1(i)′ signal point arrangements in theI-Q plane are FIG. 3A through FIG. 3C. The modulation method is QPSK.Assume, for example, that in FIG. 29A (0, 0) is transmitted as S1(i)information at time i. The signal points at this time are as shown inFIG. 3A. Then (0, 0) is transmitted as information at time as shown inFIG. 3B, for example. The same applies to (0, 1), (1, 0), and (1, 1).The time i+1 signal point arrangement is not limited to that shown inFIG. 3B, and the signal point arrangement in FIG. 3C may be usedinstead.

Thus in receiving apparatus 2700, to consider carrier 1, since themodulated signal signal point arrangements are different at time i andtime i+1, the modulated signal A and modulated signal B demodulationprecision differs at time i and time i+1.

Therefore, the modulated signal B demodulation precision can be improvedby demodulating modulated signal A at a time when the demodulationprecision is good, and then performing modulated signal B demodulationusing that result. That is to say, demodulation precision can beimproved for both modulated signals A and B.

The operation of transmitting apparatus 2600 when modulated signals Aand B with the frame configurations in FIG. 29A and FIG. 29B are formedby transmitting apparatus 2600 will now be explained.

A frame configuration signal generation section 2623 outputs FIG. 29Aand FIG. 29B frame configuration information as frame configurationsignal 2624. Coding section 2602 has transmit digital signal 2601 andframe configuration signal 2624 as input, codes transmit digital signal2601 in accordance with the modulated signal A frame configuration inFIG. 29A, and outputs post-coding transmit digital signal 2603.

Modulation section 2625 has post-coding transmit digital signal 2603 andframe configuration signal 2624 as input, and outputs transmitquadrature baseband signal 2626 in accordance with the modulated signalA frame configuration in FIG. 29A.

A serial/parallel conversion section 2604 has transmit quadraturebaseband signal 2626 and frame configuration signal 2624 as input, andoutputs a parallel signal 2605. Modulation section 2625 may beconfigured as shown in FIG. 5, for example.

In FIG. 5, mapping section X 402 maps signal points as shown in FIG. 3A.Mapping section Y 404 maps signal points as shown in FIG. 3B or FIG. 3C.

For example, in the frame configurations in FIG. 29A and FIG. 29B, toconsider carrier 1, when frame configuration signal 2624 indicates amodulated signal A, carrier 1, time i symbol, mapping section X 402executes mapping on the input digital signal, and outputs first mappedtransmit quadrature baseband signal 403.

On the other hand, when frame configuration signal 2624 indicates amodulated signal A, carrier 1, time i+1 symbol, mapping section Y 404executes mapping on the input digital signal, and outputs second mappedtransmit quadrature baseband signal 405.

Signal selection section 407 has first mapped transmit quadraturebaseband signal 403, second mapped transmit quadrature baseband signal405, and frame configuration signal 324 as input, selects the signalindicated by frame configuration signal 324, and outputs selectedtransmit quadrature baseband signal 305.

Here, as an example, a case has been described in which coding isperformed using the frame configurations in FIG. 29A and FIG. 29B—thatis, time i and time i+1—but implementation is possible in the same waywhen coding is performed at times i and i+n as in FIG. 31A and FIG. 31B.That is to say, implementation is possible in the same way, consideringan above-described time i+1 operation as a time i+n operation.

Also, the description has focused on carrier 1, but implementation ispossible in the same way when coding is similarly executed for carriersother than carrier 1.

Next, the receiving apparatus configuration will be described, FIG. 28shows the configuration of a receiving apparatus according to thisembodiment. Receiving antenna 2701 in FIG. 28 corresponds to antenna 109in FIG. 2B, and receiving antenna 2711 corresponds to antenna 110 inFIG. 2B.

The operation for carrier 1 is described below as an example. Modulatedsignal A transmission path estimation section 2707 in FIG. 28 findscarrier 1 channel fluctuation h11(t) (where t designates the time) usingmodulated signal A, carrier 1, time i radio wave propagation environmentestimation symbol 2801 in FIG. 29A. Similarly, modulated signal Btransmission path estimation section 2709 finds carrier 1 channelfluctuation h12(t) using modulated signal B, carrier 1, time i radiowave propagation environment estimation symbol 2801 in FIG. 29B.Modulated signal A transmission path estimation section 2717 findscarrier 1 channel fluctuation h21(t) (where t designates the time) usingmodulated signal A, carrier 1, time i radio wave propagation environmentestimation symbol 2801 in FIG. 29A. Similarly, modulated signal Btransmission path estimation section 2719 finds carrier 1 channelfluctuation h22(t) using modulated signal B, carrier 1, time i radiowave propagation environment estimation symbol 2801 in FIG. 29B.

Then, at time i, if the carrier 1 signal received by receiving antenna2701 is designated R1(i), and the carrier 1 signal received by receivingantenna 2711 is designated R2(i), equation (1) holds true. Similarly, attime i+1, equation (2) holds true. S1(i) and S2(i) can be obtained fromthe relationship in equation (1), and S1(i)′ and S2(i+1) can be obtainedfrom the relationship in equation (2).

Also, h11(i)≈h11(i+1), h12(i)≈h12(i+1), h21(i)≈h21(i+1), andh22(i)≈h22(i+1). At this time, the matrices of equation (1) and equation(2) are almost equal matrices, but the (S1(i), S2(i)) and (S1(i)′,S2(i+1)) vectors are different, and therefore the likelihoods of theobtained data are different.

This embodiment makes use of this characteristic to improve receive dataquality. The actual demodulation (decoding) procedure of receivingapparatus 2700 is as follows.

<1> Time i detection is performed, and (S1(i), S2(i)) is obtained.<2> Time i+1 detection is performed, and (S1(i)′, S2(i+1)) is obtained.<3> The time i and time i+1 reception qualities are compared.

If the time i reception quality is better, (S1(i), S2(i)) data obtainedin time i detection is used directly. Then S2(i+1) data is obtained byestimating S1(i)′ of time i+1 from S1(i) obtained in time i detection,and using that result.

On the other hand, if the time i+1 reception quality is better, (S1(i)′,S2(i+1)) data obtained in time i+1 detection is used directly. ThenS2(i) data is obtained by estimating S1(i) of time i from S1(i)′obtained in time i+1 detection, and using that result.

In receiving apparatus 2700, modulated signal A received digital signal2722 and modulated signal B received digital signal 2723 are obtained byperforming this kind of demodulation processing in demodulation section2721.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8, and its operation is described below.

In FIG. 8, signal 508 corresponds to 2708 in FIG. 28, signal 510corresponds to 2710 in FIG. 28, signal 506 corresponds to 2706 in FIG.28, signal 518 corresponds to 2718 in FIG. 28, signal 520 corresponds to2720 in FIG. 28, and signal 516 corresponds to 2716 in FIG. 28.

As an example, a case will here be described in which transmittingapparatus 2600 in FIG. 27 transmits both modulated signal A andmodulated signal B as QPSK modulated signals. The following descriptionrelates to carrier 1.

It is possible to transmit a total of 4 bits: 2 bits in modulated signalA and 2 bits in modulated signal B. That is to say, it is possible totransmit 0000, 0001, . . . , 1111. It is assumed that the upper 2 bitsare the 2 bits transmitted in modulated signal A, and the lower 2 bitsare the 2 bits transmitted in modulated signal B.

The operation of demodulation section 2721 in FIG. 28 will now beexplained.

For carrier 1 and time i, demodulation section 2721 finds signal pointsin the 16 signal point (0000, 0001, . . . , 1111) I-Q plane using themodulated signal A transmission path estimation signal group 2708carrier 1 component and modulated signal B transmission path estimationsignal group 2710 carrier 1 component. The state at this timecorresponds to the 16 signal points 1302 in FIG. 14.

Then demodulation section 2721 finds the reception state in the I-Qplane from the post-Fourier-transform signal 2706 carrier 1 component.The state at this time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all thesignal points indicated by reference code 1302 in FIG. 14. That is tosay, the square of the distance between signal point 1302 of transmitbits 0000 and signal point 1301 (X0000(i)) is found, and in the same waythe squares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (X0001(i), . . . , X1111(i))are found.

Similarly, for carrier 1 and time i in FIG. 29A and FIG. 29B,demodulation section 2721 finds signal points in the 16 signal point(0000, 0001, . . . , 1111) I-Q plane using the modulated signal Atransmission path estimation signal group 2718 carrier 1 component andmodulated signal B transmission path estimation signal group 2720carrier 1 component. The state at this time corresponds to the 16 signalpoints 1302 in FIG. 14.

Then demodulation section 2721 finds the reception state in the I-Qplane from the post-Fourier-transform signal 2716 carrier 1 component.The state at this time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all thesignal points indicated by reference code 1302 in FIG. 14. That is tosay, the square of the distance between signal point 1302 of transmitbits 0000 and signal point 1301 (Y0000(i)) is found, and in the same waythe squares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (Y0001(i), . . . , Y1111(i))are found.

Demodulation section 2721 then finds the sum of X0000(i) and Y0000(i),Z0000(i)=X0000(i)+Y0000(i), and similarly finds Z0001(i), . . . ,Z1111(i). In the same way, demodulation section 2721 finds Z0000(i+1),Z0001 (+1), . . . , Z1111(i+1) for time i+1.

Next, demodulation section 2721 compares the likelihoods of time i andtime i+1 receive data.

For example, demodulation section 2721 searches for the smallest valueamong Z0000(i), Z0001(i), . . . , Z1111(i). Let that value be designatedF(i). Then demodulation section 2721 searches for the second-smallestvalue. Let that value be designated S(i).

Similarly, demodulation section 2721 searches for the smallest valueamong Z0000(i+1), Z0001(i+1), . . . , Z1111(i+1). Let that value bedesignated F(i+1). Then demodulation section 2721 searches for thesecond-smallest value. Let that value be designated S(i+1).

Then, for example, demodulation section 2721 finds R(i)=F(i)/S(i), andR(i+1)=F(i+1)/S(i+1).

When R(i+1)>R(i), demodulation section 2721 determines that the time ireception quality is better, and determines that the 4 bits providingF(i) are correct data. Then the 2 data bits transmitted in modulatedsignal A at time i and time i+1 and the 2 data bits transmitted inmodulated signal B at time i are obtained. The 2 bits transmitted inmodulated signal B at time i+1 are then determined making use of thefact that the 2 bits transmitted in modulated signal A have beendetermined. For example, if the 2 bits transmitted in modulated signal Aare 00, the 2 bits transmitted in modulated signal B at time i+1 aredetermined by searching for the item with the smallest value amongZ0000(i+1), Z0001(i+1), Z0010(i+1), and Z0011(i+1). Similarly, if the 2bits transmitted in modulated signal A are 01, the 2 bits transmitted inmodulated signal B at time i+1 are determined by searching for the itemwith the smallest value among Z0100(i+1), Z0101(i+1), Z0110(i+1), andZ0111(i+1). The 2 bits transmitted in modulated signal B at time i+1 arealso determined in the same way when the 2 bits transmitted in modulatedsignal A are 10 or 11.

When R(i)>R(i+1), demodulation section 2721 determines that the time 1reception quality is better, and determines that the 4 bits providingF(i+1) are correct data. Then the 2 data bits transmitted in modulatedsignal A at time i and time i+1 and the 2 data bits transmitted inmodulated signal B at time i+1 are obtained. The 2 bits transmitted inmodulated signal B at time i are then determined making use of the factthat the 2 bits transmitted in modulated signal A have been determined.For example, if the 2 bits transmitted in modulated signal A are 00, the2 bits transmitted in modulated signal B at time i are determined bysearching for the item with the smallest value among Z0000(i), Z0001(i),Z0010(i), and Z0011(i). Similarly, if the 2 bits transmitted inmodulated signal A are 01, the 2 bits transmitted in modulated signal Bat time i are determined by searching for the item with the smallestvalue among Z0100(i), Z0101(i), Z0110(i), and Z0111(i). The 2 bitstransmitted in modulated signal B at time i are also determined in thesame way when the 2 bits transmitted in modulated signal A are 10 or 11.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8. Operations in FIG. 8 are described below.

As described above, modulated signal A and B demodulation section 608 inFIG. 8 outputs data transmitted in modulated signal A at time i and timei+1 as modulated signal A received digital signal 524. Also, modulatedsignal A and B demodulation section 608 outputs Z0000(i), . . . ,Z1111(i) as first soft decision value signal 701, and outputsZ0000(i+1), . . . , Z1111(i+1) as second soft decision value signal 702.Furthermore, modulated signal A and B demodulation section 608 outputsreceived digital signal 525-1 of modulated signal B of either time i ortime i+1.

Modulated signal B demodulation section 703 has Z0000(i), . . . ,Z1111(i) comprising first soft decision value signal 701 and Z0000(i+1),. . . , Z1111(i+1) comprising second soft decision value signal 702 asinput, and, as described above, performs modulated signal B demodulationbased on the time i and time i+1 reception qualities, and outputsmodulated signal B received digital signal 525-2 of a different timefrom 525-1.

Although the carrier 1 decoding method has been described here, decodingcan be performed in the same way when coding is similarly performed in acarrier other than carrier 1 if the above operations are considered asbeing for the other carrier. That is to say, carrier a decoding can beperformed by means of the FIG. 28 post-Fourier-transform signal carriern component, modulated signal A transmission path estimation signalgroup carrier n component, and modulated signal B transmission pathestimation signal group carrier n component. Next, a case in which theframe configurations shown in FIG. 31A and FIG. 31B are used will bedescribed. With the frame configurations shown in FIG. 31A and FIG. 31B,coding is performed at times i and i+n. Therefore, if n is such that therelationships h11(i)≈h11(i+n), h12(i)≈h12(i+n), h21(i)≈h21(i+n), andh22(i)≈h22(i+n) hold true, implementation is possible by carrying outthe same kind of processing as with the frame configurations in FIG. 29Aand FIG. 29B. That is to say, operations can be executed in the same wayas in the description for FIG. 29A and FIG. 29B, considering a time i+1operation as a time i+n operation.

Next, a case in which the frame configurations shown in FIG. 33A andFIG. 33B are used will be described. At this time, the fact that thetimes at times i and j are totally different, and therefore the radiowave propagation environments are totally different, is important.

The operation for carrier 1 is described below as an example. At time i,equation (1) holds true. Similarly, at time j, equation (3) holds true.At this time, in the receiving apparatus, h11(i), h12(i), h21(i), andh22(i) are estimated using, for example, carrier 1 time i−1 radio wavepropagation environment estimation symbol 2801 in FIG. 33A. Similarly,in the receiving apparatus, h11(j), h12(j), h21(j), and h22(j) areestimated using, for example, carrier 1 time j−1 radio wave propagationenvironment estimation symbol 2801 in FIG. 33B. Here, since the radiowave propagation environment differs greatly for times i and j,h11(i)≠h11(j), h12(i)≠h12(j), h21(i)≠h21(j), and h22(i)≠h22(j).Therefore, time i and j reception qualities are totally different.

A description will now be given of signal point arrangements in the I-Qplane for time i and time j taking the above into consideration.Examples of modulated signal A signal point arrangements in the I-Qplane are shown in FIG. 3A through FIG. 3C. When the frameconfigurations shown in FIG. 33A and FIG. 33B are used, the time i and jsignal point arrangements may, for example, both be as shown in FIG. 3A,or may differ, with the time i signal point arrangement as shown in FIG.3A and the time j signal point arrangement as shown in FIG. 3B. This isbecause, unlike in the case of the frame configurations in FIG. 29A,FIG. 29B, FIG. 31A, and FIG. 31B, the radio wave propagation environmentdiffers for times i and j, and therefore the reception quality isdifferent at times i and j even if the signal point arrangement is notintentionally varied.

The decoding procedure is described in detail below. This can beconsidered as similar to the operation in the case of the frameconfigurations in FIG. 29A and FIG. 29B. That is to say, time i+1operations can be thought of as being replaced by time j operations.

The actual demodulation (decoding) procedure performed by receivingapparatus 2700 on signals with the frame configurations shown in FIG.33A and FIG. 33B is as follows.

<1> Time i detection is performed, and (S1(i), S2(i)) is obtained.<2> Time j detection is performed, and (S1(i), S2(j)) is obtained.<3> The time i and time j reception qualities are compared.

If the time i reception quality is better, (S1(i), S2(i)) data isobtained in time i detection. Then S1(i) of time j is estimated fromS1(i) obtained in time i detection, and S2(j) is obtained using thatresult.

If the time j reception quality is better, (S1(i), S2(j)) data isobtained in time j detection. Then S1(i) of time i is estimated fromS1(i) obtained in time j detection, and S2(i) is obtained using thatresult.

In demodulation section 2721 in FIG. 28, modulated signal A receiveddigital signal 2722 and modulated signal B received digital signal 2723are obtained by performing the above procedure.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8, and its operation is described below.

In FIG. 8, signal 508 corresponds to 2708 in FIG. 28, signal 510corresponds to 2710 in FIG. 28, signal 506 corresponds to 2706 in FIG.28, signal 518 corresponds to 2718 in FIG. 28, signal 520 corresponds to2720 in FIG. 28, and signal 516 corresponds to 2716 in FIG. 28.

As an example, a case will here be described in which transmittingapparatus 2600 in FIG. 27 transmits both modulated signal A andmodulated signal B as QPSK modulated signals in carrier 1 using theframe configurations in FIG. 33A and FIG. 33B.

It is possible to transmit a total of 4 bits: 2 bits in modulated signalA and 2 bits in modulated signal B. That is to say, it is possible totransmit 0000, 0001, . . . , 1111. It is assumed that the upper 2 bitsare the 2 bits transmitted in modulated signal A, and the lower 2 bitsare the 2 bits transmitted in modulated signal B.

The operation of demodulation section 2721 in FIG. 28 will now beexplained.

At time i, demodulation section 2721 finds signal points in the 16signal point (0000, 0001, . . . , 1111) I-Q plane using the modulatedsignal A transmission path estimation signal group 2708 carrier 1component and modulated signal B transmission path estimation signalgroup 2710 carrier 1 component. The state at this time corresponds tothe 16 signal points 1302 in FIG. 14. Then demodulation section 2721finds the reception state in the I-Q plane from thepost-Fourier-transform signal 2706 carrier 1 component. The state atthis time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all thesignal points indicated by reference code 1302 in FIG. 14. That is tosay, the square of the distance between signal point 1302 of transmitbits 0000 and signal point 1301 (X0000(i)) is found, and in the same waythe squares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (X0001(i), . . . , X1111(i))are found.

Similarly, at time i in FIG. 33A and FIG. 33B, demodulation section 2721finds signal points in the 16 signal point (0000, 0001, . . . , 1111)I-Q plane using the modulated signal A transmission path estimationsignal group 2718 carrier 1 component and modulated signal Btransmission path estimation signal group 2720 carrier 1 component. Thestate at this time corresponds to the 16 signal points 1302 in FIG. 14.

Then demodulation section 2721 finds the reception state in the I-Qplane from the post-Fourier-transform signal 2716 carrier 1 component.The state at this time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all thesignal points indicated by reference code 1302 in FIG. 14. That is tosay, the square of the distance between signal point 1302 of transmitbits 0000 and signal point 1301 (Y0000(i)) is found, and in the same waythe squares of the distances between signal points 1302 of transmit bits0001, . . . , 1111 and signal point 1301 (Y0001(i), . . . , Y1111(i))are found.

Demodulation section 2721 then finds the sum of X0000(i) and Y0000(i),Z0000(i)=X0000(i)+Y0000(i), and similarly finds Z0001(i), . . . ,Z1111(i). In the same way, demodulation section 2721 finds Z0000(j),Z0001(j), . . . , Z1111(j) for time j.

Here, when time i determination is performed, radio wave propagationenvironment estimation is performed using, for example, the FIG. 33A andFIG. 33B time i−1 radio wave propagation environment estimation symbol2801 carrier 1 symbols. On the other hand, when time j determination isperformed, radio wave propagation environment estimation is performedusing, for example, the FIG. 33A and FIG. 33B time j−1 radio wavepropagation environment estimation symbol 2801 carrier 1 symbols.

Next, demodulation section 2721 compares the likelihoods of time i andtime j receive data.

For example, demodulation section 2721 searches for the smallest valueamong Z0000(i), Z0001(i), . . . , Z1111(i). Let that value be designatedF(i). Then demodulation section 2721 searches for the second-smallestvalue. Let that value be designated S(i).

Similarly, demodulation section 2721 searches for the smallest valueamong Z0000(j), Z0001 (j), . . . , Z1111(j). Let that value bedesignated F(j). Then demodulation section 2721 searches for thesecond-smallest value. Let that value be designated S(j).

Then, for example, demodulation section 2721 finds R(i)=F(i)/S(i), andR(j)=F(j)/S(j).

When R(j)>R(i), demodulation section 2721 determines that the time ireception quality is better, and determines that the 4 bits providingF(i) are correct data. Then the 2 data bits transmitted in modulatedsignal A at time i and time j and the 2 data bits transmitted inmodulated signal B at time i are obtained. The 2 bits transmitted inmodulated signal B at time j are then determined making use of the factthat the 2 bits transmitted in modulated signal A have been determined.For example, if the 2 bits transmitted in modulated signal A are 00, the2 bits transmitted in modulated signal B at time j are determined bysearching for the item with the smallest value among Z0000(j), Z0001(j),Z0010(j), and Z0011(j). Similarly, if the 2 bits transmitted inmodulated signal A are 01, the 2 bits transmitted in modulated signal Bat time j are determined by searching for the item with the smallestvalue among Z0100(j), Z0101(j), Z0110(j), and Z0111(j). The 2 bitstransmitted in modulated signal B at time j are also determined in thesame way when the 2 bits transmitted in modulated signal A are 10 or 11.

When R(i)>R(j), demodulation section 2721 determines that the time jreception quality is better, and determines that the 4 bits providingF(j) are correct data. Then the 2 data bits transmitted in modulatedsignal A at time i and time j and the 2 data bits transmitted inmodulated signal B at time j are obtained. The 2 bits transmitted inmodulated signal B at time i are then determined making use of the factthat the 2 bits transmitted in modulated signal A have been determined.For example, if the 2 bits transmitted in modulated signal A are 00, the2 bits transmitted in modulated signal B at time i are determined bysearching for the item with the smallest value among Z0000(i), Z0001(i),Z0010(i), and Z0011(i). Similarly, if the 2 bits transmitted inmodulated signal A are 01, the 2 bits transmitted in modulated signal Bat time i are determined by searching for the item with the smallestvalue among Z0100(i), Z0101(i), Z0110(i), and Z0111(i). The 2 bitstransmitted in modulated signal B at time i are also determined in thesame way when the 2 bits transmitted in modulated signal A are 10 or 11.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8. Operations in FIG. 8 are described below.

As described above, modulated signal A and B demodulation section 608 inFIG. 8 outputs data transmitted in modulated signal A at time i and timej as modulated signal A received digital signal 524. Also, modulatedsignal A and B demodulation section 608 outputs Z0000(i), . . . ,Z1111(i) as first soft decision value signal 701, and outputs Z0000(j),. . . , Z1111(j) as second soft decision value signal 702. Furthermore,modulated signal A and B demodulation section 608 outputs receiveddigital signal 525-1 of modulated signal B of either time i or time j.

Modulated signal B demodulation section 703 has Z0000(i), . . . ,Z1111(i) comprising first soft decision value signal 701 and Z0000(j), .. . , Z1111(j) comprising second soft decision value signal 702 asinput, and, as described above, performs modulated signal B demodulationbased on the time i and time j reception qualities, and outputsmodulated signal B received digital signal 525-2 of a different timefrom 525-1.

Although carrier 1 time i and time j modulated signal A and modulatedsignal B demodulation has been described here, implementation ispossible by carrying out the same kind of processing when coding issimilarly performed in a carrier other than carrier 1.

Next, a detailed description will be given of a case where coding isperformed in the frequency axis direction, which is possible when usinga multicarrier system such as OFDM. That is to say, items on whichabove-described coding in the time axis direction is performed aresubjected to coding in the frequency axis direction. Next, a case inwhich the frame configurations shown in FIG. 30A and FIG. 30B are usedwill be described. Characteristics of the frame configurations in FIG.30A and FIG. 30B are that modulated signal A transmits the same data bymeans of symbols S1(i) and S1(i)′ with different signal pointarrangements in carrier 1 and carrier 2 at time i, while modulatedsignal B transmits different data by means of symbols S2(i−1) andS2(i−2) in carrier 1 and carrier 2 at time i.

Drawings showing the S1(i) and S1(i)′ signal point arrangements in theI-Q plane are FIG. 3A through FIG. 3C. The modulation method is QPSK.Assume, for example, that in FIG. 30A (0, 0) is transmitted as S1(i)information in carrier 1 at time i.

The signal points at this time are as shown in FIG. 3A. Then (0, 0) istransmitted as information in carrier 2 at time i as shown in FIG. 3B,for example. The same applies to (0, 1), (1, 0), and (1, 1). The carrier2, time i signal point arrangement is not limited to that shown in FIG.3B, and transmission may also be performed using the signal pointarrangement in FIG. 3C. Thus, at time i, the same information istransmitted with different signal point arrangements in carrier 1 andcarrier 2.

Thus in the receiving apparatus, to consider time i, since the receivedmodulated signal signal point arrangements are different in carrier 1and carrier 2, the carrier 1 modulated signal A and modulated signal Bdemodulation precision and the carrier 2 modulated signal A andmodulated signal B demodulation precision are different. The modulatedsignal B demodulation precision can then be improved by demodulatingmodulated signal A at a time when the demodulation precision is good,and then performing modulated signal B demodulation using that result.That is to say, demodulation precision can be improved for bothmodulated signals A and B. The operation of transmitting apparatus 2600when modulated signals A and B with the frame configurations in FIG. 30Aand FIG. 30B are formed by transmitting apparatus 2600 will now beexplained.

Frame configuration signal generation section 2623 outputs FIG. 30A andFIG. 30B frame configuration information as frame configuration signal2624. Coding section 2602 has transmit digital signal 2601 and frameconfiguration signal 2624 as input, codes transmit digital signal 2601in accordance with the modulated signal A frame configuration in FIG.30A, and outputs post-coding transmit digital signal 2603.

Modulation section 2625 has post-coding transmit digital signal 2603 andframe configuration signal 2624 as input, and outputs transmitquadrature baseband signal 2626 in accordance with the modulated signalA frame configuration in FIG. 30A. Modulation section 2625 may beconfigured as shown in FIG. 5, for example.

In FIG. 5, mapping section X 402 maps signal points as shown in FIG. 3A.Mapping section Y 404 maps signal points as shown in FIG. 3B or FIG. 3C.

For example, in the frame configurations in FIG. 30A and FIG. 30B, toconsider time i, when frame configuration signal 2624 indicates amodulated signal A, carrier 1, time i symbol, mapping section X 402executes mapping on the input digital signal, and outputs first mappedtransmit quadrature baseband signal 403.

On the other hand, when frame configuration signal 2624 indicates amodulated signal A, carrier 2, time i symbol, mapping section Y 404executes mapping on the input digital signal, and outputs second mappedtransmit quadrature baseband signal 405.

Signal selection section 407 has first mapped transmit quadraturebaseband signal 403, second mapped transmit quadrature baseband signal405, and frame configuration signal 324 as input, selects the signalindicated by frame configuration signal 324, and outputs selectedtransmit quadrature baseband signal 305.

Here, as an example, a ease has been described in which coding isperformed using the frame configurations in FIG. 30A and FIG. 30B—thatis, across carrier 1 and carrier 2 at time i—but implementation ispossible in the same way when coding is performed across carrier 1 andcarrier n as in FIGS. 32A and FIG. 32B. That is to say, implementationis possible in the same way, considering an above-described carrier 2operation as a carrier n operation. Also, the description has focused ontime i, but implementation is possible in the same way when coding issimilarly executed at times other than time i, and furthermoreimplementation is also possible in the same way when coding is executedacross carriers other than carrier 1 and carrier 2 at time i.

Next, the receiving apparatus configuration will be described. FIG. 28shows the configuration of a receiving apparatus according to thisembodiment. Receiving antenna 2701 in FIG. 28 corresponds to antenna 109in FIG. 2B, and receiving antenna 2711 corresponds to antenna 110 inFIG. 2B.

The operation at time i is described below as an example. A descriptionwill first be given for carrier 1. Modulated signal A transmission pathestimation section 2707 in FIG. 28 finds carrier 1 channel fluctuationh11,1(t) (where t designates the time) using modulated signal A, carrier1, time i radio wave propagation environment estimation symbol 2801 inFIG. 30A. Similarly, modulated signal B transmission path estimationsection 2709 finds carrier 1 channel fluctuation h12,1(t) usingmodulated signal B, carrier 1, time i radio wave propagation environmentestimation symbol 2801 in FIG. 30B. Modulated signal A transmission pathestimation section 2717 finds carrier 1 channel fluctuation h21,1(t)using modulated signal A, carrier 1, time i radio wave propagationenvironment estimation symbol 2801 in FIG. 30A. Similarly, modulatedsignal B transmission path estimation section 2719 finds carrier 1channel fluctuation h22,1(t) using modulated signal B, carrier 1, time iradio wave propagation environment estimation symbol 2801 in FIG. 30B.

Then, at time i, if the carrier 1 signal received by receiving antenna2701 is designated R1,1(i), and the carrier 1 signal received byreceiving antenna 2711 is designated R2,1(i), the following equationholds true.

$\begin{matrix}{\begin{pmatrix}{{R\; 1},{1(i)}} \\{{R\; 2},{1(i)}}\end{pmatrix} = {\begin{pmatrix}{{h\; 11},{1(i)}} & {{h\; 12},{1(i)}} \\{{h\; 21},{1(i)}} & {{h\; 22},{1(i)}}\end{pmatrix}\begin{pmatrix}{S\; 1(i)} \\{S\; 2\left( {i - 1} \right)}\end{pmatrix}}} & (11)\end{matrix}$

Similarly, for carrier 2, the following equation holds true.

$\begin{matrix}{\begin{pmatrix}{{R\; 1},{2(i)}} \\{{R\; 2},{2(i)}}\end{pmatrix} = {\begin{pmatrix}{{h\; 11},{2(i)}} & {{h\; 12},{2(i)}} \\{{h\; 21},{2(i)}} & {{h\; 22},{2(i)}}\end{pmatrix}\begin{pmatrix}{S\; 1(i)^{\prime}} \\{S\; 2\left( {i - 2} \right)}\end{pmatrix}}} & (12)\end{matrix}$

S1(i) and S2(i−1) can be obtained from the relationship in equation(11), and S1(i)′ and S2(i−2) can be obtained from the relationship inequation (12).

Also, h11,1(i)≈h11,2(i), h12,1(i)≈h12,2(i), h21,1(i)≈h21,2(i), andh22,1(i)≈h22,2(i). At this time, the matrices of equation (11) andequation (12) are almost equal matrices, but the (S1(i), S2(i−1)) and(S1(i)′, S2(i−2)) vectors are different, and therefore the likelihoodsof the obtained data are different.

This embodiment makes use of this characteristic to improve receive dataquality. The actual demodulation (decoding) procedure of receivingapparatus 2700 is as follows.

<1> Time i, carrier 1 detection is performed, and (S1(i), S2(i−1)) isobtained.<2> Time i, carrier 2 detection is performed, and (S1(i)′, S2(i−2)) isobtained.<3> The carrier 1 and carrier 2 reception qualities are compared.

If the carrier 1 reception quality is better, (S1(i), S2(i−1)) data isobtained in carrier 1 detection. Then S1(i)′ of carrier 2 is estimatedfrom S1(i) obtained in carrier 1 detection, and S2(i−2) is obtainedusing that result.

If the carrier 2 reception quality is better, (S1(i)′, S2(i−2)) data isobtained in carrier 2 detection. Then S1(i) of carrier 1 is estimatedfrom S1(i)′ obtained in carrier 2 detection, and S2(i−1) is obtainedusing that result.

In receiving apparatus 2700, modulated signal A received digital signal2722 and modulated signal B received digital signal 2723 are obtained byperforming this kind of demodulation processing in demodulation section2721.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8, and its operation is described below.

In FIG. 8, signal 508 corresponds to 2708 in FIG. 28, signal 510corresponds to 2710 in FIG. 28, signal 506 corresponds to 2706 in FIG.28, signal 518 corresponds to 2718 in FIG. 28, signal 520 corresponds to2720 in FIG. 28, and signal 516 corresponds to 2716 in FIG. 28.

As an example, a case will here be described in which transmittingapparatus 2600 in FIG. 27 performs QPSK modulation for both modulatedsignal A and modulated signal B using the frame configurations in FIG.30A and FIG. 30B. The following description relates to carrier 1 andcarrier 2.

It is possible to transmit a total of 4 bits: 2 bits in modulated signalA and 2 bits in modulated signal B. That is to say, it is possible totransmit 0000, 0001, . . . , 1111. It is assumed that the upper 2 bitsare the 2 bits transmitted in modulated signal A, and the lower 2 bitsare the 2 bits transmitted in modulated signal B.

The operation of demodulation section 2721 in FIG. 28 will now beexplained.

For carrier 1 and time i, demodulation section 2721 finds signal pointsin the 16 signal point (0000, 0001, . . . , 1111) I-Q plane using themodulated signal A transmission path estimation signal group 2708carrier 1 component and modulated signal B transmission path estimationsignal group 2710 carrier 1 component. The state at this timecorresponds to the 16 signal points 1302 in FIG. 14.

Then demodulation section 2721 finds the reception state in the I-Qplane from the post-Fourier-transform signal 2706 carrier 1 component.The state at this time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all signalpoints 1302 shown in FIG. 14. That is to say, the square of the distancebetween signal point 1302 of transmit bits 0000 and signal point 1301(X0000(i)) is found, and in the same way the squares of the distancesbetween signal points 1302 of transmit bits 0001, . . . , 1111 andsignal point 1301 (X0001(i), . . . , X1111(i)) are found.

Similarly, for carrier 1 and time i in FIG. 30A and FIG. 30B,demodulation section 2721 finds signal points in the 16 signal point(0000, 0001, . . . , 1111) I-Q plane using the modulated signal Atransmission path estimation signal group 2718 carrier 1 component andmodulated signal B transmission path estimation signal group 2720carrier 1 component. The state at this time corresponds to the 16 signalpoints 1302 in FIG. 14.

Then demodulation section 2721 finds the reception state in the I-Qplane from the post-Fourier-transform signal 2716 carrier 1 component.The state at this time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all signalpoints 1302 shown in FIG. 14. That is to say, the square of the distancebetween signal point 1302 of transmit bits 0000 and signal point 1301(Y0000(i)) is found, and in the same way the squares of the distancesbetween signal points 1302 of transmit bits 0001, . . . , 1111 andsignal point 1301 (Y0001(i), . . . , Y1111(i)) are found.

Demodulation section 2721 then finds the sum of X0000(i) and Y0000(i),Z0000(i)=X0000(i)+Y0000(i), and similarly finds Z0001(i), . . . ,Z1111(i). In the same way, demodulation section 2721 finds Z0000(i),Z0001(i), . . . , Z1111(i) for carrier 2.

Next, demodulation section 2721 compares the likelihoods of carrier 1and carrier 2 receive data.

For example, in carrier 1, demodulation section 2721 searches for thesmallest value among Z0000(i), Z0001(i), . . . , Z1111(i). Let thatvalue be designated F(i). Then demodulation section 2721 searches forthe second-smallest value. Let that value be designated S(i).

Similarly, in carrier 2, demodulation section 2721 searches for thesmallest value among Z0000(i), Z0001(i), . . . , Z1111(i). Let thatvalue be designated F(i). Then demodulation section 2721 searches forthe second-smallest value. Let that value be designated S(i).

Then, for example, demodulation section 2721 finds R,1(i)=F(i)/S(i) forcarrier 1, and R,2(i)=F(i)/S(i) for carrier 2.

When R,2(i)>R,1(i), demodulation section 2721 determines that thecarrier 1 reception quality is better, and determines that the 4 bitsproviding carrier 1 F(i) are correct data. Then the 2 data bitstransmitted in modulated signal A in carrier 1 and carrier 2 and the 2data bits transmitted in carrier 1 modulated signal B are obtained. The2 bits transmitted in carrier 2 modulated signal B at time i+1 are thendetermined making use of the fact that the 2 bits transmitted inmodulated signal A have been determined. For example, if the 2 bitstransmitted in modulated signal A are 00, the 2 bits transmitted incarrier 2 modulated signal B are determined by searching for the itemwith the smallest value among carrier 2 Z0000(i), Z0001(i), Z0010(i),and Z0011(i). Similarly, if the 2 bits transmitted in modulated signal Aare 01, the 2 bits transmitted in carrier 2 modulated signal B aredetermined by searching for the item with the smallest value amongcarrier 2 Z0100(i), Z0101(i), Z0110(i), and Z0111(i). The 2 bitstransmitted in carrier 2 modulated signal B are also determined in thesame way when the 2 bits transmitted in modulated signal A are 10 or 11.

When R,1(i)>R,2(i), demodulation section 2721 determines that thecarrier 2 reception quality is better, and determines that the 4 bitsproviding carrier 2 F(i) are correct data. Then the 2 data bitstransmitted in modulated signal A in carrier 1 and carrier 2 and the 2data bits transmitted in carrier 2 modulated signal B are obtained. The2 bits transmitted in carrier 1 modulated signal B are then determinedmaking use of the fact that the 2 bits transmitted in modulated signal Ahave been determined. For example, if the 2 bits transmitted inmodulated signal A are 00, the 2 bits transmitted in carrier 1 modulatedsignal B are determined by searching for the item with the smallestvalue among carrier 1 Z0000(i), Z0001(i), Z0010(i), and Z0011(i).Similarly, if the 2 bits transmitted in modulated signal A are 01, the 2bits transmitted in carrier 1 modulated signal B are determined bysearching for the item with the smallest value among carrier 1 Z0100(i),Z0101(i), Z0110(i), and Z0111(i). The 2 bits transmitted in carrier 1modulated signal B are also determined in the same way when the 2 bitstransmitted in modulated signal A are 10 or 11.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8. Operations in FIG. 8 are described below.

As described above, modulated signal A and B demodulation section 608 inFIG. 8 outputs data transmitted in modulated signal A in time i carrier1 and carrier 2 as modulated signal A received digital signal 524. Also,modulated signal A and B demodulation section 608 outputs carrier 1Z0000(i), . . . , Z1111(i) as first soft decision value signal 701, Z1111(i) as second soft decision value signal 702. Furthermore, modulatedsignal A and B demodulation section 608 outputs received digital signal525-1 of modulated signal B of either time i carrier 1 or carrier 2.

Modulated signal B demodulation section 703 has carrier 1 Z0000(i), . .. , Z1111(i) comprising first soft decision value signal 701 and carrier2 Z0000(i), . . . , Z1111(i) comprising second soft decision valuesignal 702 as input, and, as described above, performs modulated signalB demodulation based on the carrier 1 and carrier 2 reception qualities,and outputs modulated signal B received digital signal 525-2 of adifferent carrier from 525-1.

Although the decoding method for carrier 1 and carrier 2 has beendescribed here, decoding can be performed in the same way by similarlyexecuting the above-described operations when coding is similarlyperformed in carriers other than carrier 1 and carrier 2.

When the frame configurations shown in FIG. 32A and FIG. 32B are used,if n is such that the relationships h11,1(i)≈h11,1+n(i),h12,1(i)≈h12,1+n(i), h21,1(i)≈h21,1+n(i), and h22,1(i)□h22,1+n(i) holdtrue, implementation is possible by carrying out the same kind ofprocessing as with the frame configurations in FIG. 30A and FIG. 30B.That is to say, operations can be executed in the same way, consideringa carrier 2 operation as a carrier 1+n operation.

Next, a case in which the frame configurations shown in FIG. 34A andFIG. 34B are used will be described. In the case of frame configurationsin FIG. 34A and FIG. 34B, the fact that the frequencies of carrier 1 andcarrier j are totally different, and therefore the radio wavepropagation environments are totally different, is important.

Here, the case of carrier 1 and carrier j will be described as anexample. For time i and carrier 1, equation (11) holds true. For time iand carrier j, the following equation holds true.

$\begin{matrix}{\begin{pmatrix}{{R\; 1},{j(i)}} \\{{R\; 2},{j(i)}}\end{pmatrix} = {\begin{pmatrix}{{h\; 11},{j(i)}} & {{h\; 12},{j(i)}} \\{{h\; 21},{j(i)}} & {{h\; 22},{j(i)}}\end{pmatrix}\begin{pmatrix}{S\; 1(i)^{\prime}} \\{S\; 2\left( {i - j} \right)}\end{pmatrix}}} & (13)\end{matrix}$

At this time, in the receiving apparatus, h11,1(i), h12,1(i), h21,1(i),and h22,1(i) are estimated using, for example, carrier 1 time i−1 radiowave propagation environment estimation symbols 2801 in FIG. 34A andFIG. 34B. Similarly, in the receiving apparatus, h11,j(i), h12,j(i),h21,j(i), and h22,j(i) are estimated using, for example, carrier j timei−1 radio wave propagation environment estimation symbols 2801 in FIG.34A and FIG. 34B. At this time, since the times are such that the radiowave propagation environment differs for carrier 1 and carrier j,h11,1(i)≠h11,j(i), h12,1(i)≠h12,j(i), h21,1(i)≠h21,j(i), andh22,1(i)≠h22,j(i). Therefore, carrier 1 and j reception qualities aretotally different.

A description will now be given of signal point arrangements in the I-Qplane for carrier 1 and carrier j taking the above into consideration.Examples of modulated signal A signal point arrangements in the I-Qplane are shown in FIG. 3A through FIG. 3C. When the frameconfigurations shown in FIG. 34A and FIG. 34B are used, the carrier 1and carrier j signal point arrangements may, for example, both be asshown in FIG. 3A, or may differ, with the carrier 1 signal pointarrangement as shown in FIG. 3A and the carrier j signal pointarrangement as shown in FIG. 3B. This is because, unlike in the case ofthe frame configurations in FIG. 29A, FIG. 29B, FIG. 31A, and FIG. 31B,the radio wave propagation environment differs for carrier 1 and carrierj, and there is therefore a difference in reception quality betweencarrier 1 and carrier j even if the signal point arrangement is notintentionally varied.

The decoding procedure is described in detail below. This can beconsidered as similar to the operation in the case of the frameconfigurations in FIG. 30A and FIG. 30B.

That is to say, carrier 2 operations can be thought of as being replacedby carrier j operations.

The actual demodulation (decoding) procedure performed by receivingapparatus 2700 on signals with the frame configurations shown in FIG.34A and FIG. 34B is as follows.

<1> Time i, carrier 1 detection is performed, and (S1(i), S2(i−1)) isobtained.<2> Time i, carrier j detection is performed, and (S1(i), S2(i−j)) isobtained.<3> The carrier 1 and carrier j reception qualities are compared.

If the time i, carrier 1 reception quality is better, (S1(i), S2(i−1))data is obtained in time i, carrier 1 detection. Then S1(i) of time i,carrier j is estimated from S1(i) obtained in time i, carrier 1detection, and S2(i−j) is obtained using that result.

If the time i, carrier j reception quality is better, (S1(i), S2(i−j))data is obtained in time i, carrier j detection. Then S1(i) of time i,carrier 1 is estimated from S1(i) obtained in time i, carrier jdetection, and S2(i−1) is obtained using that result.

In demodulation section 2721 in FIG. 28, modulated signal A receiveddigital signal 2722 and modulated signal B received digital signal 2723are obtained by performing the above procedure.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8, and its operation is described below.

In FIG. 8, signal 508 corresponds to 2708 in FIG. 28, signal 510corresponds to 2710 in FIG. 28, signal 506 corresponds to 2706 in FIG.28, signal 518 corresponds to 2718 in FIG. 28, signal 520 corresponds to2720 in FIG. 28, and signal 516 corresponds to 2716 in FIG. 28.

As an example, a case will here be described in which transmittingapparatus 2600 in FIG. 27 performs transmission employing QPSKmodulation for both modulated signal A and modulated signal B in carrier1 and carrier j using the frame configurations in FIG. 34A and FIG. 34B.

It is possible to transmit a total of 4 bits: 2 bits in modulated signalA and 2 bits in modulated signal B. That is to say, it is possible totransmit 0000, 0001, . . . , 1111. It is assumed that the upper 2 bitsare the 2 bits transmitted in modulated signal A, and the lower 2 bitsare the 2 bits transmitted in modulated signal B.

The operation of demodulation section 2721 in FIG. 28 will now beexplained.

At time i, demodulation section 2721 finds signal points in the 16signal point (0000, 0001, . . . , 1111) I-Q plane using the modulatedsignal A transmission path estimation signal group 2708 carrier 1component and modulated signal B transmission path estimation signalgroup 2710 carrier 1 component. The state at this time corresponds tothe 16 signal points 1302 in FIG. 14.

Then demodulation section 2721 finds the reception state in the I-Qplane from the post-Fourier-transform signal 2706 carrier 1 component.The state at this time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all signalpoints 1302 shown in FIG. 14. That is to say, the square of the distancebetween signal point 1302 of transmit bits 0000 and signal point 1301(X0000(i)) is found, and in the same way the squares of the distancesbetween signal points 1302 of transmit bits 0001, . . . , 1111 andsignal point 1301 (X0001(i), . . . , X1111(i)) are found.

Similarly, at time i in FIG. 34A and FIG. 34B, demodulation section 2721finds signal points in the 16 signal point (0000, 0001, . . . , 1111)I-Q plane using the modulated signal A transmission path estimationsignal group 2718 carrier 1 component and modulated signal Btransmission path estimation signal group 2720 carrier 1 component. Thestate at this time corresponds to the 16 signal points 1302 in FIG. 14.

Then demodulation section 2721 finds the reception state in the I-Qplane from the post-Fourier-transform signal 2716 carrier 1 component.The state at this time corresponds to signal point 1301 in FIG. 14.

Next, demodulation section 2721 calculates, for example, the square ofthe distance in the I-Q plane between signal point 1301 and all signalpoints 1302 shown in FIG. 14. That is to say, the square of the distancebetween signal point 1302 of transmit bits 0000 and signal point 1301(Y0000(i)) is found, and in the same way the squares of the distancesbetween signal points 1302 of transmit bits 0001, . . . , 1111 andsignal point 1301 (Y0001(i), . . . , Y1111(i)) are found.

Demodulation section 2721 then finds the sum of X0000(i) and Y0000(i),Z0000(i)=X0000(i)+Y0000(i), and similarly finds Z0001(i), . . . ,Z1111(i). Here, when time i determination is performed, radio wavepropagation environment estimation is performed using, for example, theFIG. 34A and FIG. 34B time i−1 radio wave propagation environmentestimation symbol 2801 carrier 1 and carrier j symbols.

Next, demodulation section 2721 compares the likelihoods of time icarrier 1 and carrier j receive data.

For example, demodulation section 2721 searches for the smallest valueamong carrier 1 Z0000(i), Z0001(i), . . . , Z1111(i). Let that value bedesignated F(i). Then demodulation section 2721 searches for thesecond-smallest value. Let that value be designated S(i).

Similarly, demodulation section 2721 searches for the smallest valueamong carrier j Z0000(i), Z0001(i), . . . , Z1111(i). Let that value bedesignated F(i). Then demodulation section 2721 searches for thesecond-smallest value. Let that value be designated S(i). Then, forexample, demodulation section 2721 finds carrier 1 R(i)=F(i)/S(i), andcarrier j R(i)=F(i)/S(i).

When carrier j R(i)>carrier 1 R(i), demodulation section 2721 determinesthat the carrier 1 reception quality is better, and determines that the4 bits providing carrier 1 F(i) are correct data.

Then the 2 data bits transmitted in modulated signal A in carrier 1 andcarrier j and the 2 data bits transmitted in carrier 1 modulated signalB are obtained. The 2 bits transmitted in carrier j modulated signal Bare then determined making use of the fact that the 2 bits transmittedin modulated signal A have been determined. For example, if the 2 bitstransmitted in modulated signal A are 00, the 2 bits transmitted incarrier j modulated signal B are determined by searching for the itemwith the smallest value among carrier j Z0000(i), Z0001(i), Z0010(i),and Z0011(i).

Similarly, if the 2 bits transmitted in modulated signal A are 01, the 2bits transmitted in carrier j modulated signal B are determined bysearching for the item with the smallest value among carrier j Z0100(i),Z0101(i), Z0110(i), and Z0111(i). The 2 bits transmitted in carrier jmodulated signal B are also determined in the same way when the 2 bitstransmitted in modulated signal A are 10 or 11. When carrier 1R(i)>carrier j R(i), demodulation section 2721 determines that thecarrier j reception quality is better, and determines that the 4 bitsproviding carrier j F(i) are correct data.

Then the 2 data bits transmitted in carrier 1 and carrier j modulatedsignal A and the 2 data bits transmitted in carrier j modulated signal Bare obtained.

The 2 bits transmitted in carrier 1 modulated signal B are thendetermined making use of the fact that the 2 bits transmitted inmodulated signal A have been determined. For example, if the 2 bitstransmitted in modulated signal A are 00, the 2 bits transmitted incarrier 1 modulated signal B are determined by searching for the itemwith the smallest value among carrier 1 Z0000(i), Z0001(i), Z0010(i),and Z0011(i). Similarly, if the 2 bits transmitted in modulated signal Aare 01, the 2 bits transmitted in carrier 1 modulated signal B aredetermined by searching for the item with the smallest value amongcarrier 1 Z0100(i), Z0101(i), Z0110(i), and Z0111(i). The 2 bitstransmitted in modulated signal B at time i are also determined in thesame way when the 2 bits transmitted in modulated signal A are 10 or 11.

The detailed configuration of demodulation section 2721 in FIG. 28 is asshown in FIG. 8. Operations in FIG. 8 are described below.

As described above, modulated signal A and B demodulation section 608 inFIG. 8 outputs data transmitted in modulated signal A in carrier 1 andcarrier j as modulated signal A received digital signal 524. Also,modulated signal A and B demodulation section 608 outputs carrier 1Z0000(i), . . . , Z1111(i) as first soft decision value signal 701, andoutputs carrier j Z0000(i), . . . , Z1111(i) as second soft decisionvalue signal 702. Furthermore, modulated signal A and B demodulationsection 608 outputs received digital signal 525-1 of modulated signal Bof either carrier 1 or carrier j.

Modulated signal B demodulation section 703 has carrier 1 Z0000(i), . .. , Z1111(i) comprising first soft decision value signal 701 and carrierj Z0000(i), . . . , Z1111(i) comprising second soft decision valuesignal 702 as input, and, as described above, performs modulated signalB demodulation based on the carrier 1 and carrier j reception qualities,and outputs modulated signal B received digital signal 525-2 of adifferent carrier from 525-1.

Although time i carrier 1 and carrier j modulated signal A and modulatedsignal B demodulation has been described here, implementation ispossible by carrying out the same kind of processing when coding issimilarly performed in carriers other than carrier 1 and carrier j.

FIG. 35A and FIG. 35B show sample frame configurations when the frameconfigurations in FIG. 10A are applied to an OFDM system. Implementationis also similarly possible for an OFDM system by carrying out the samekind of processing as for FIG. 10A frame configuration signals describedin Embodiment 1.

FIG. 36A and FIG. 36B show frame configurations when coding is performedin the frequency axis direction, as opposed to the time direction codingof the frame configurations in FIG. 35A and FIG. 35B. The processing forFIG. 36A and FIG. 36B frame configuration signals can be implemented bycombining the processing described in Embodiment 1 and the processingdescribed in this embodiment.

FIG. 37A and FIG. 37B show sample frame configurations when the frameconfigurations in FIG. 10B are applied to an OFDM system. Implementationis also similarly possible for an OFDM system by carrying out the samekind of processing as for FIG. 10B frame configuration signals describedin Embodiment 1.

FIG. 38A and FIG. 38B show frame configurations when coding is performedin the frequency axis direction, as opposed to the time direction codingof the frame configurations in FIG. 37A and FIG. 37B. The processing forFIG. 38A and FIG. 38B frame configuration signals can be implemented bycombining the processing described in Embodiment 1 and the processingdescribed in this embodiment.

FIG. 39A through FIG. 39C show sample frame configurations when theframe configurations in FIG. 15 are applied to an OFDM system.Implementation is also similarly possible for an OFDM system by carryingout the same kind of processing as for FIG. 15 frame configurationsignals described in Embodiment 2.

FIG. 40A through FIG. 40C show frame configurations when coding isperformed in the frequency axis direction, as opposed to the timedirection coding of the frame configurations in FIG. 39A through FIG.39C. The processing for FIG. 40A through FIG. 40C frame configurationsignals can be implemented by combining the processing described inEmbodiment 2 and the processing described in this embodiment.

FIG. 41A through FIG. 41C show sample frame configurations when theframe configurations in FIG. 16 are applied to an OFDM system.Implementation is also possible for an OFDM system by carrying out thesame kind of implementation as in Embodiment 2.

FIG. 42A through FIG. 42C show frame configurations when coding isperformed in the frequency axis direction, as opposed to the timedirection coding of the frame configurations in FIG. 41A through FIG.41C. The processing for FIG. 42A through FIG. 42C frame configurationsignals can be implemented by combining the processing described inEmbodiment 2 and the processing described in this embodiment.

FIG. 43A through FIG. 43C show sample frame configurations when theframe configurations in FIG. 22 are applied to an OFDM system.Implementation is also possible for an OFDM system by carrying out thesame kind of implementation as in Embodiment 2.

FIG. 44A through FIG. 44C show frame configurations when coding isperformed in the frequency axis direction, as opposed to the timedirection coding of the frame configurations in FIG. 43A through FIG.43C. The processing for FIG. 44A through FIG. 44C frame configurationsignals can be implemented by combining the processing described inEmbodiment 2 and the processing described in this embodiment.

FIG. 45A through FIG. 45C show sample frame configurations when theframe configurations in FIG. 26 are applied to an OFDM system.Implementation is also possible for an OFDM system by carrying out thesame kind of implementation as in Embodiment 2.

FIG. 46A through FIG. 46C show frame configurations when coding isperformed in the frequency axis direction, as opposed to the timedirection coding of the frame configurations in FIG. 45A through FIG.45C. The processing for FIG. 46A through FIG. 46C frame configurationsignals can be implemented by combining the processing described inEmbodiment 2 and the processing described in this embodiment.

In FIG. 35A and FIG. 35B, FIG. 36A and FIG. 36B, FIG. 39A through FIG.39C, FIG. 40A through FIG. 40C, FIG. 43A through FIG. 43C, and FIG. 44Athrough FIG. 44C, examples have been described of coding as adjacentsymbols along the time or frequency axis, but the present invention isnot limited to this, and implementation is similarly possible for casesof 2, 3, . . . , n symbol separation.

The configuration of the transmitting apparatus is not limited to theconfiguration in FIG. 27, and the configuration of the modulationsection is not limited to the configuration in FIG. 5. Also, theconfigurations of the receiving apparatus and demodulation section arenot limited to the configurations in FIG. 8 and FIG. 28.

(4) Embodiment 4

In above Embodiments 1 through 3, it has mainly been proposed that atleast one modulated signal among modulated signals transmitted fromrespective antennas be formed by modulating the same data a plurality oftimes while changing the signal point arrangement mode in the timedirection or the frequency direction.

In this embodiment, the present invention is described as beingeffective in a case such as a line-of-sight environment if the signalpoint arrangement mode is changed in the time direction or frequencydirection for at least one modulated signal, even though the signalpoint arrangement mode of the same data is not changed.

In this embodiment a modulated signal is formed without modulating thesame data a plurality of times, enabling data transmission efficiency tobe improved compared with Embodiments 1 through 3.

In this embodiment, as a preferred example, it is proposed that, inaddition to Embodiments 1 through 3, interleaving processing be furtherexecuted on transmit data, and the signal point arrangement mode bechanged in predetermined block units.

FIG. 47A and FIG. 47B show an example of the application of interleavingaccording to this embodiment. FIG. 47A shows the order of data prior tointerleaving, and FIG. 47B shows the data sequence after interleaving.In the example shown in FIG. 47A and FIG. 47B, interleaving is performedvertically by reading data sequentially from left to right.Specifically, data is rearranged into the following order: data 1, data101, data 201, data 2, data 102, data 202, . . . , data 100, data 200,data 300 (this data sequence being termed “pattern X”).

FIG. 48A through FIG. 48C show sample signal point arrangements of datarearranged as shown in FIG. 47B. FIG. 48A, FIG. 48B, and FIG. 48C eachshow sample signal point arrangements of modulated signal A andmodulated signal B.

Here, I-Q plane signal point arrangements of the first through 100thsymbols of pattern X are assumed to be as shown in FIG. 48A formodulated signals A and B. At this time, the phase formed between asignal point and the I-axis is assumed to be 45 degrees for bothmodulated signals A and B.

I-Q plane signal point arrangements of the 101st through 200th symbolsof pattern X are assumed to be as shown in FIG. 48B for modulatedsignals A and B. At this time, the phase formed between a signal pointand the I-axis is assumed to be 45 degrees for modulated signal A and 0degrees for modulated signal B.

I-Q plane signal point arrangements of the 201st through 300th symbolsof pattern X are assumed to be as shown in FIG. 48C for modulatedsignals A and B. At this time, the phase formed between a signal pointand the I-axis is assumed to be 45 degrees for modulated signal A and45+10 degrees for modulated signal B.

In this embodiment a case has been described in which 300 symbols aredivided into three, but if 300 symbols are divided into m groups, thephase formed by a modulated signal A signal point and the I-axis isfixed at 45 degrees, and the phase formed by a modulated signal B signalpoint and the I-axis changes progressively as follows: 45 degrees, 0degrees, 45+10 degrees, 10 degrees, . . . .

That is to say:

1) the phase formed by a modulated signal B signal point and the I-axisin the (2n−1)'th change of the signal point arrangement is 10n−10degrees, and2) the phase formed by a modulated signal B signal point and the I-axisin the 2n'th change of the signal point arrangement is 45+10n degrees,where n=1, 2, . . . . Thus, in this embodiment, the signal pointarrangement mode is changed in predetermined block units. By this means,the effect of performing interleaving is obtained with the signal pointarrangement mode, enabling time diversity gain to be obtained. Thereason for this is explained by the operation of the receivingapparatus.FIG. 49, in which parts corresponding to those in FIG. 4 are assignedthe same codes as in FIG. 4, shows a sample configuration of atransmitting apparatus according to this embodiment. A coding section4802 has a transmit digital signal 4801 as input, performs coding suchas convolutional coding, turbo coding, or LDPC (Low Density ParityCheck) coding on transmit digital signal 4801, and outputs a post-codingdigital signal 4803.

An interleaving section 4804 has post-coding digital signal 4803 andframe configuration signal 324 as input, performs interleaving such asshown in FIG. 47A and FIG. 47B, for example, on post-coding digitalsignal 4803, and outputs a post-interleaving digital signal 4805.

Modulation section 304 has post-interleaving digital signal 4805 andframe configuration signal 324 as input, and outputs transmit quadraturebaseband signal 305. The detailed configuration of modulation section304 is as shown in FIG. 50.

In FIG. 50, a mapping section 4902 has a post-interleaving digitalsignal 4901 and frame configuration signal 4906 as input, performs QPSKmodulation in accordance with signal point arrangements such as shown inFIG. 48A, for example, on post-interleaving digital signal 4901, andoutputs an quadrature baseband signal 4903.

A signal processing section (rotation computation section) 4904 hasquadrature baseband signal 4903 and frame configuration signal 4906 asinput, performs phase rotation so as to produce different signal pointarrangements in predetermined block units as described above, andoutputs a post-phase-rotation quadrature baseband signal 4905.

Coding section 4807 and interleaving section 4809 in FIG. 49 perform thesame kind of operations as described above. Modulation section 314 has apost-interleaving digital signal as input, performs QPSK modulation, andoutputs transmit quadrature baseband signal 315. At this time,modulation section 314 does not change the signal point arrangement formodulated signal B as shown in FIG. 48A, and therefore, unlikemodulation section 304, need not have the signal processing section(rotation computation section) 4904 shown in FIG. 50.

FIG. 51 shows a sample configuration of a receiving apparatus accordingto this embodiment. Parts in FIG. 51 that operate in the same way as inFIG. 6 are assigned the same codes as in FIG. 6. An MLD (MaximumLikelihood Detection) section 523 finds a branch metric by findingcandidate signal points, receive baseband signals, and Euclidiandistances, and outputs a modulated signal A soft decision value 5001 andmodulated signal B soft decision value 5002.

A de-interleaving section 5003 has modulated signal A soft decisionvalue 5001 as input, de-interleaves this, and outputs apost-de-interleaving modulated signal A soft decision value 5004. Adecoding section 5005 has post-de-interleaving modulated signal A softdecision value 5004 as input, performs soft decision decoding of this,and outputs a modulated signal A received digital signal 5006.

Similarly, a de-interleaving section 5007 has modulated signal B softdecision value 5002 as input, de-interleaves this, and outputs apost-de-interleaving modulated signal B soft decision value 5008. Adecoding section 5009 has post-de-interleaving modulated signal B softdecision value 5008 as input, performs soft decision decoding of this,and outputs a modulated signal B received digital signal 5010.

Incidentally, a line-of-sight propagation environment will beconsidered. At this time, the channel matrix in equation (1) can beconsidered divided into direct wave component elements h11,d, h12,d,h21,d, h22,d, and scattered wave component elements h11,s, h12,s, h21,s,h22,s, and can be expressed by the following equation.

$\begin{matrix}{\begin{pmatrix}{Rx}_{1} \\{Rx}_{2}\end{pmatrix} = {{\left( {{\rho_{d}\begin{pmatrix}h_{11,d} & h_{12,d} \\h_{21,d} & h_{22,d}\end{pmatrix}} + {\rho_{r}\begin{pmatrix}h_{11,s} & h_{12,s} \\h_{21,s} & h_{22,s}\end{pmatrix}}} \right)\begin{pmatrix}{Tx}_{a} \\{Tx}_{b}\end{pmatrix}} + \begin{pmatrix}n_{1} \\n_{2}\end{pmatrix}}} & (14)\end{matrix}$

It is known that, if the direct wave elements fall into a stationarystate, this indicates that the reception quality is totally differentaccording to that state even if the received field strength is the same(see, for example, the document “Analysis of a MIMO System in Relationto Rice Fading,” IEICE Technical Report RCS 2003-90, pp. 1-6, July2003). In a line-of-sight environment in which direct waves arepredominant, in particular, there is a possibility of a stationary statearising in which the effect of interleave patterns between modulatedsignals being made to differ is not fully evident.

When such a state is entered, satisfactory error rate performances areunlikely to be obtained even if the received field strength issufficient. This is because cases arise in which the reception qualityis poor due to the state of the direct wave matrix in equation (14) eventhough the received field strength is sufficient.

In this embodiment, the signal point arrangement mode of at least onemodulated signal is varied, enabling the above-described degradation ofreception quality to be improved. This is particularly suitable forcases where convolutional coding or the like is used and soft decisionsare made in the receiving apparatus. The apparatus configuration andoperation are as described above. The reason why reception qualityimproves when the above-described kind of configuration is used will nowbe explained in detail.

In FIG. 52A and FIG. 52B, reference code 5101 denotes signal points whena modulated signal A and B composite signal is received, and when bothmodulated signals A and B are QPSK signals as in FIG. 48A through FIG.48C, there are 16 candidate signal points as shown in FIG. 52A and FIG.52B. In FIG. 52A and FIG. 52B, reference code 5102 denotes virtualsignal points when only modulated signal A is provisionally received. Inactuality, since modulated signals A and B are transmittedsimultaneously, the four 5102 points do not become candidate signalpoints.

It is here assumed that, when modulated signals such as shown in FIG.48A are transmitted, the signal point arrangement is as shown in FIG.52A in the receiving apparatus. Looking at the minimum Euclidiandistance at this time, there are places where this is extremely small.

In a line-of-sight environment in which direct waves are predominant,when modulated signal A and modulated signal B are transmitted in thestate shown in FIG. 48A, they continue to be received in this state, andgood-quality data cannot be received if soft decision decoding isperformed in this state.

To avoid this, in this embodiment, for example, modulated signal B isrotated through −45 degrees with respect to the arrangement in FIG. 48Aas shown in FIG. 48B, and is rotated through 10 degrees with respect tothe arrangement in FIG. 48A as shown in FIG. 48C. Then, whentransmission is performed as shown in FIG. 48C, for example, thereceived signal points have the kind of signal point arrangement shownin FIG. 52B, the minimum Euclidian distances are increased, andreception quality is improved. When modulated signal B is subjected tovarious phase rotations in an environment in which direct waves arepredominant, a variety of Euclidian distances are created, enabling aneffect similar to a diversity effect to be obtained. This enables thequality of receive data to be improved.

As described above, in this embodiment a time diversity effect isobtained by forming at least one modulated signal while varying thesignal point arrangement mode in the time direction, enabling receivedata with improved error rate performances to be obtained.

In addition, a synergistic effect of interleaving together with changingof the signal point arrangement mode every interleave block makes itpossible to prevent the Euclidian distances between candidate signalpoints and reception points becoming extremely small, enabling receivedata with still further improved error rate performances to be obtained.

The angles through which the modulated signal B signal point arrangementis rotated are not limited to those mentioned above. However, if only 90degree, 180 degree, and 270 degree angles of rotation are used, thereceived signal candidate signal point arrangement will not change, andtherefore no effect will be obtained. Using angles of rotation from 0degrees to 45 degrees or from −45 degrees to 0 degrees will achieveuniversality, and fixing the angles within this range will enable theconfigurations of rotation computation section 4904 in transmittingapparatus 4800 and MLD section 523 in receiving apparatus 5000 to besimplified.

In the above description, only modulated signal B is rotated, butimplementation is possible in the same way if modulated signal A is alsorotated. However, the effective improvement in reception quality doesnot differ greatly when both modulated signals are rotated and when onlyone is rotated. Therefore, from the standpoint of simplifying theconfigurations of rotation computation section 4904 in transmittingapparatus 4800 and MLD section 523 in receiving apparatus 5000, it isbetter to rotate only one modulated signal.

Next, descriptions will be given of different transmission methods fromthat described above.

As shown in FIG. 53A and FIG. 53B, the modulated signal B signal pointarrangement at time T+i is rotated through θ_(i) degrees with respect tothe signal point arrangement at time T. An example is considered here inwhich rotation is not applied to modulated signal A. In FIG. 53A andFIG. 53B, the relationship between the time i signal point arrangementand time i+1 signal point arrangement for modulated signal B is shown,this being assumed to be θ_(i)−θ_(i-1)=10 degrees.

With this kind of transmission, as described above, in an environment inwhich direct waves are predominant the Euclidian distances betweenreceived signal points and candidate signal points are various, enablingan effect similar to a diversity effect to be obtained. This enables theerror rate performances of receive data to be improved.

Also, if the relationship between the time i signal point arrangementand time i+1 signal point arrangement is made a fixed value ofθ_(i)−θ_(i-1)=10 degrees as in the example given here, theconfigurations of rotation computation section 4904 in transmittingapparatus 4800 and MLD section 523 in receiving apparatus 5000 can besimplified.

If θ_(i)−θ_(i-1) is made 0, 90, 180, or 270 degrees, the positionalrelationships of candidate signal points in MLD section 523 of receivingapparatus 5000 do not vary between time i and time i+1, and there is nochange in the relationships of Euclidian distances between receivedsignal points and candidate signal points. As receiving apparatus 5000consequently does not obtain a diversity effect and there is littleeffect of improving the data error rate, these are not suitable anglesof rotation. Thinking along the same lines, it is also difficult toobtain a diversity effect if θ_(i)−θ_(i-1) is made 45, 105, 225, or 315degrees, and therefore these are also unsuitable values.

There is one kind of positional relationship of candidate signal pointsin the MLD section of the receiving apparatus when θ_(i)−θ_(i-1) is 0,90, 180, or 270 degrees, and two kinds when θ_(i)−θ_(i-1) is 45, 105,225, or 315 degrees, and a diversity effect is also difficult to obtainin these cases. That is to say, no very significant diversity effect isobtained using conventional QPSK or π/4 shift QPSK. However, this is notto say that there is no diversity effect at all.

In terms of setting suitable values, the design should provide forreceived signal candidate signal points to have a plurality of signalpoint arrangements (a plurality of minimum Euclidian distances).Possible examples include 5 degrees (angles providing the same kind ofreceived signal candidate signal point arrangements as 5 degrees include95, 185, 275, . . . , and 90/5=18 kinds of received signal candidatesignal point arrangements are provided); 10 degrees (angles providingthe same kind of received signal candidate signal point arrangements as10 degrees include 100, 190, 280, . . . , and 90/10=9 kinds of receivedsignal candidate signal point arrangements are provided); and 15 degrees(angles providing the same kind of received signal candidate signalpoint arrangements as 15 degrees include 105, 195, 285, . . . , and90/15=6 kinds of received signal candidate signal point arrangements areprovided). Other suitable values are those for which exact 90/x divisionis not possible.

In the above description, a case has been described in which only phaserotation is applied, but the signal point arrangement mode may also bechanged by switching transmission power. Moreover, it is also possibleto use a combination of transmission power and phase rotation. FIGS. 54Aand FIG. 54B show sample received signal candidate signal pointarrangements when both phase rotation and transmission power switchingare used. Euclidian distance relationships, and minimum Euclidiandistances in particular, can also be changed in the same way asdescribed above when both phase rotation and transmission powerswitching are used. By this means a diversity effect can be obtained andreceive data error rate performances can be improved.

A method is also possible whereby coding is performed and phase rotationis effected for one modulated signal, while coding is not performed forthe other modulated signal. This corresponds to the implementation oftrellis coding modulation in a MIMO system proposed in “Channel codingwith multilevel/phase signals,” IEEE Transaction on Information Theory,vol. IT-28, pp. 55-67, January 1982. Trellis coding modulation isdesigned so that constraints are imposed on signal point transitions byperforming coding, and by this means transition of signal points withdistant Euclidian distances is performed.

In order to obtain an effect equivalent to this, it is important in aMIMO system to effect phase rotation. To consider two slots, forexample, if the phase is rotated the signal point arrangements receivedat time T and time T+1 are different, and consequently the Euclidiandistances are different. Therefore, effecting phase rotation andperforming coding enable constraints to be imposed on signal pointtransitions in the same way as trellis coding modulation.

In this embodiment a case has been described in which spread spectrumcommunication is performed, but this is not a limitation, andimplementation is also possible in the same way when there is nospreading section or despreading section—that is, for a single-carriersystem. Application is also possible in the same way to a multicarriersystem such as OFDM. In this case, in addition to a method that forms amodulated signal whose phase has been rotated in the time direction, theapproach of changing the signal point arrangement in the time axisdirection can also be extended to the frequency axis direction.Specifically, a different signal point arrangement (for example,rotation) can be provided for each subcarrier (carrier). A methodwhereby unique phase rotation is used for each subcarrier can beconsidered as an example of a simple configuration in this case. That isto say, with respect to the signal point arrangement of subcarrier 0,phase rotation of θ1 is applied to subcarrier 1, θ2 to subcarrier 2, . .. , and θn to subcarrier n. By this means a diversity effect can beobtained in the subcarrier direction (frequency direction), enablingreceive data error rate performances to be improved in the same way aswhen a diversity effect is obtained in the time direction.

In this embodiment, implementation is also possible in the same way whenLDPC, turbo coding, or the like is used as well as convolutional coding.

(5) Embodiment 5

In this embodiment it is proposed that feedback information indicatingthe modulated signal reception state be received from the communicatingparty, and the signal point arrangement mode be changed based on thisfeedback information.

FIG. 55 shows a sample configuration of a base station according to thisembodiment. Parts in FIG. 55 that operate in the same way as in FIG. 49are assigned the same codes as in FIG. 49.

Base station 5400 receives a signal transmitted from a terminal at anantenna 5401. A receiving apparatus 5403 has the received signal 5402received by antenna 5401 as input, demodulates this signal, and outputsa received digital signal 5404.

A signal point arrangement decision section 5405 has received digitalsignal 5404 as input, extracts feedback information from this receiveddigital signal 5404, decides the signal point arrangement from thisfeedback information, and outputs a signal point arrangement controlsignal 5406.

Modulation sections 304 and 314 perform signal point arrangement basedon this signal point arrangement control signal 5406.

Here, base station 5400 sends the terminal information on the signalpoint arrangement mode implemented by modulation sections 304 and 314.Specifically, base station 5400 includes information on the signal pointarrangement mode implemented during modulation in the transmit signals.The feedback information, signal point arrangement control method, andterminal operation will be described in detail later herein.

FIG. 56 shows a sample configuration of a communication terminalaccording to this embodiment. Parts in FIG. 56 that operate in the sameway as in FIG. 51 are assigned the same codes as in FIG. 51.

MLD section 523 outputs received signal point status information 5501based on modulated signal A transmission path estimation signals 508 and518, and modulated signal B transmission path estimation signals 510 and520. Suitable items for received signal point status information 5501include the minimum Euclidian distance or eigenvalue status, ormodulated signal A and B transmission path estimation signals, but arenot limited to these. For example, a signal indicating the presence orabsence of an error, such as ACK/NACK information, may also be used asreceived signal point status information 5501.

A feedback information generation section 5502 has received signal pointstatus information 5501 as input, and outputs feedback information 5503based on this input. The base station 5400 signal point arrangement modemay also be decided in advance by feedback information generationsection 5502, and transmitted as feedback information 5503. That is tosay, the signal point arrangement mode may also be decided bycommunication terminal 5500.

A transmitting apparatus 5505 has feedback information 5503 and atransmit digital signal 5504 as input, performs predetermined radioprocessing on these, and outputs a transmit signal 5506. Transmit signal5506 is output from a transmitting antenna 5507.

Next, the signal point arrangement control method will be explained.Assume, for example, that base station 5400 transmits modulated signalsA and B as shown in FIG. 53A, and that communication terminal 5500receives these modulated signals in the state shown in FIG. 52A. Thisstate is known from received signal point status information 5501comprising information such as the minimum Euclidian distance oreigenvalue status, or modulated signal A and B transmission pathestimation signals, output from MLD section 523. A signal pointarrangement mode such that the minimum Euclidian distance becomes largeas in FIG. 52B is then decided by base station 5400 or communicationterminal 5500, and base station 5400 performs modulation processing inaccordance with the decided signal point arrangement. For example, basestation 5400 may perform modulation while switching the signal pointarrangement mode from that shown in FIG. 53A to that shown in FIG. 53B.

By receiving feedback information indicating the modulated signalreception state and changing the signal point arrangement based on thefeedback information, as described above, the signal point arrangementmode can be changed according to the reception state, enabling theminimum Euclidian distance to be made significantly larger, and receivedata error rate performances to be greatly improved. A particularlymarked effect is obtained in an environment in which direct waves arepredominant, in the same way as in Embodiment 4.

In this embodiment a case has been described in which spread spectrumcommunication is performed, but this is not a limitation, andimplementation is also possible in the same way when there is nospreading section or despreading section—that is, for a single-carriersystem. Moreover, implementation is also possible in the same way for amulticarrier system such as OFDM.

Phase rotation is not the only way of changing the signal pointarrangement mode, and as described in other embodiments, the same kindof effect can also be obtained by changing the transmission power. Inthis case, the transmission power alone may be changed, or bothtransmission power and phase rotation changes may be used.

The present invention also enables the same kind of effect as describedabove to be obtained when applied, for example, to a MIMO system inwhich transmit signals are transmitted in multi-beam form, such asdescribed in “A MIMO Channel Eigenbeam Space Division Multiplexing(E-SDM) System,” IEICE Technical Report RCS 2002-53, May 2002.

FIG. 57 shows the general configuration of this kind of MIMO system. Onthe transmitting side, a modulation section 5701 has a transmit datastream as input, and forms a plurality of modulated signals bymodulating this transmit data stream. Here, modulation section 5701performs modulation processing by changing the signal point arrangementmode the time direction or in the frequency direction for at least onemodulated signal, as described in above Embodiments 1 through 5.

A channel analysis section 5702 calculates a plurality of transmitchannel signature vectors for forming a multiplex channel based onchannel status information comprising propagation channel estimationresults. A vector multiplexing section 5703 multiplies together andcombines individual channel signature vectors and modulated signals, andsends signals after combining to a transmitting array antenna 5704. Bythis means, multi-beam signals are transmitted from transmitting arrayantenna 5704.

On the receiving side, a channel analysis section 5711 calculates aplurality of receive channel signature vectors for separatingmultiplexed modulated signals based on channel status informationcomprising propagation channel estimation results. A multiplex signalseparation section 5713 has received signals from a receiving arrayantenna 5712 as input, and by multiplying received signals by therespective channel signature vectors, separates signals in which aplurality of received signals are multiplexed into a plurality ofreceived modulated signals. A signal processing section 5714 obtainsreceive data by demodulating and decoding the separated receivedmodulated signals.

The present invention is not limited to above-described Embodiments 1through 5, and various variations and modifications may be possiblewithout departing from the scope of the present invention. For example,in the above embodiments cases have been described in which the presentinvention is mainly implemented by means of hardware, but the presentinvention is not limited to this, and can also be implemented by meansof software.

For example, it is also possible for a program that executes theabove-described functions to be stored in ROM (Read Only Memory)beforehand, and for this program to be run by a CPU (Central ProcessingUnit).

As described above, according to the present invention a communicationapparatus and method can be implemented that enable excellent receptionquality to be obtained while suppressing a decrease in data transmissionefficiency.

This application is based on Japanese Patent Application No. 2003-190683filed on Jul. 2, 2003, and Japanese Patent Application No. 2004-173224filed on May 14, 2004, the entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is widely applicable to radio systems thattransmit different modulated signals from a plurality of antennas, andis suitable for application to an OFDM-MIMO communication system, forexample.

1. A transmitting apparatus comprising: a signal processing section thatgenerates a plurality of modulated signals using a first mapping patternof a predetermined modulation scheme, outputs one or more of theplurality of modulated signals, which are mapped using the first mappingpattern, as a first modulated signal, and outputs a second modulatedsignal, in which the rest of the plurality of modulated signals otherthan the first modulated signal, is re-mapped using a predeterminedmapping pattern of the predetermined modulation scheme, thepredetermined mapping pattern of the predetermined modulation schemebeing one of the first mapping pattern and a plurality of second mappingpatterns, the first mapping pattern mapping a first bit set, which isone combination of a plurality of bits, to a first signal point on theIQ plane, the second mapping patterns mapping the first bit set, whichis each one combination of the plurality of bits, to second signalpoints on the IQ plane, respectively, the first signal point and thesecond signal points being different signal points on the IQ plane, adistance between the first signal point and an origin on the IQ plane isthe same as a distance between each second signal point and the originon the IQ plane, and the first bit set being selected from allcombinations possible with the plurality of bits; an OFDM conversionsection that converts the first modulated signal and the secondmodulated signal into a plurality of OFDM signals, respectively; and aplurality of antennas that transmit the plurality of OFDM signals at acommon time and in a common frequency band.
 2. The transmittingapparatus of claim 1, wherein the plurality of OFDM signals comprise thepredetermined mapping pattern used for the second modulated signal.
 3. Acommunication method comprising: generating a plurality of modulatedsignals using a first mapping pattern of a predetermined modulationscheme, outputting one or more of the plurality of modulated signals,which are mapped using the first mapping pattern, as a first modulatedsignal, and outputting a second modulated signal, in which the rest ofthe plurality of modulated signals other than the first modulatedsignal, is re-mapped using a predetermined mapping pattern of thepredetermined modulation scheme, the predetermined mapping pattern ofthe predetermined modulation scheme being one of the first mappingpattern and a plurality of second mapping patterns, the first mappingpattern mapping a first bit set, which is one combination of a pluralityof bits, to a first signal point on the IQ plane, the second mappingpatterns mapping the first bit set, which is each one combination of theplurality of bits, to a second signal points on the IQ planerespectively, the first signal point and the second signal points beingdifferent signal points on the IQ plane, a distance between the firstsignal point and an origin on the IQ plane is the same as a distancebetween each second signal point and the origin on the IQ plane, and thefirst bit set being selected from all combinations possible with theplurality of bits; converting the first modulated signal and the secondmodulated signal into a plurality of OFDM signals, respectively; andtransmitting the plurality of OFDM signals at a common time and in acommon frequency band.
 4. The communication method of claim 3, whereinthe plurality of OFDM signals comprise the predetermined mapping patternused for the second modulated signal.